Removing calls to some deprecated Sinon APIs

[hiranya911]

Addressing the deprecation warnings:

FirebaseApp
    #name
      ✓ should throw if the app has already been deleted
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
      ✓ should return the app's name
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
      ✓ should be case sensitive
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
      ✓ should respect leading and trailing whitespace
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
      ✓ should be read-only
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
    #options
      ✓ should throw if the app has already been deleted
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
      ✓ should return the app's options
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
      ✓ should be read-only
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
      ✓ should not return an object which can mutate the underlying options
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
      ✓ should ignore the config file when options is not null
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
      ✓ should throw when the environment variable points to non existing file
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
      ✓ should throw when the environment variable contains bad json
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
      ✓ should throw when the environment variable points to an empty file
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
      ✓ should throw when the environment variable points to bad json
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
      ✓ should ignore a bad config key in the config file
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
      ✓ should ignore a bad config key in the json string
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
      ✓ should not throw when the config file has a bad key and the config file is unused
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
      ✓ should not throw when the config json has a bad key and the config json is unused
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
      ✓ should use explicitly specified options when available and ignore the config file
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
      ✓ should not throw if some fields are missing
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
      ✓ should not throw when the config environment variable is not set, and some options are present
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
      ✓ should init with application default creds when no options provided and env variable is not set
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
      ✓ should init with application default creds when no options provided and env variable is an empty json
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
      ✓ should init when no init arguments are provided and config var points to a file
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
      ✓ should init when no init arguments are provided and config var is json
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
    #delete()
      ✓ should throw if the app has already been deleted
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
      ✓ should call removeApp() on the Firebase namespace internals
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
      ✓ should call delete() on each service's internals
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
    auth()
      ✓ should throw if the app has already been deleted
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
      ✓ should return the Auth namespace
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
      ✓ should return a cached version of Auth on subsequent calls
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
    messaging()
      ✓ should throw if the app has already been deleted
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
      ✓ should return the Messaging namespace
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
      ✓ should return a cached version of Messaging on subsequent calls
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
    database()
      ✓ should throw if the app has already been deleted
sinon.reset is deprecated and will be removed from the public API in a future version of sinon.
      ✓ should return the Database