cleanup: remove some unused dependencies

[suzmue]

No description provided.

[gemini-code-assist]

Code Review

This pull request performs dependency cleanup across several crates in the workspace. Specifically, it removes the unused base64 dependency from google-cloud-gax and the hyper dependency from google-cloud-storage. It also relocates the google-cloud-rpc dependency within the google-cloud-pubsub crate. I have no feedback to provide as there were no review comments to evaluate.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.76%. Comparing base (02edf0b) to head (564c547).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5638   +/-   ##
=======================================
  Coverage   97.76%   97.76%           
=======================================
  Files         221      221           
  Lines       51115    51115           
=======================================
+ Hits        49971    49973    +2     
+ Misses       1144     1142    -2     

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