Update prettier dev-dependency to v2.5.1 in Event Hub

[JonathanCrd]

Solves: #9329 for packages under sdk/eventhub.

Updated prettier dev-dependency version to latest 2.5.1.
Files were re-formatted as well. There are only format changes in this PR, no manual changes except for package.json files.

Main format changes with Prettier 2.x in this PR include:

• Trailing commas by default.
• Whitespace added after every function keyword.

[JonathanCrd]

To fix the CI, I had to remove the path "test/**/*.ts" from the format and check-format mock-hub since there is no test folder in it.

[deyaaeldeen]

Thanks for doing this!