channelz: Regenerate proto

[arjan-bal]

This change regenerated the protos using the command go generate ./... to fix the vet-proto CI test.

RELEASE NOTES: N/A

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.35%. Comparing base (3e475d7) to head (13d450e).
⚠️ Report is 4 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8872      +/-   ##
==========================================
+ Coverage   82.47%   83.35%   +0.87%     
==========================================
  Files         414      414              
  Lines       32751    32751              
==========================================
+ Hits        27011    27298     +287     
+ Misses       4089     4057      -32     
+ Partials     1651     1396     -255     

see 28 files with indirect coverage changes

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