Remove unnecessary dependencies

[JianpingChen]

Move the following dependencies from "dependencies" to "devDependencies".
"@types/node-fetch": "^2.5.0",
"@types/tunnel": "^0.0.1",

[xirzec]

Seems reasonable to me

[chradek]

@types/tunnel was moved to a devDependency once before in #4541, and moved back to a dependency in #4676, I think because the types from @types/tunnel were referenced in an exported type. Can we test that the built npm artifact still compiles when used in a project with another package (like storage-blob) before merging?

I don't know if @types/node-fetch was intentionally added as a dependency or if that can live as a dev dependency.

[daviwil]

@chradek Thanks for pulling up that PR, I was also worried that changing these might cause compiler-breaking changes. I ran API Extractor on these changes and it doesn't complain that we aren't exporting a type that is being used in either library. I also tried packing the library and using it in a very basic way, didn't see any compiler issues.

The previous issue we saw with tunnel occurred before we made the switch to node-fetch so it's possible that whatever caused it got removed when we dropped the old Axios support. I think we should be OK here but I'll wait a bit longer before merging this PR so that we can do some extra checks if necessary.

[chradek]

I downloaded @azure/core-http@1.0.0-preview.2 where we had made @types/tunnel a dependency again. @daviwil is right, the axios http client needed the types from tunnel. Now that we don't use axios I'm not concerned about tunnel given David's testing above.

[daviwil]

Thanks for the extra verification @chradek! I'll merge this now. Thanks for sending the PR @JianpingChen!