Cherry-pick #405 to garden: Fix compatibility with protobuf 22

[scpeters]

Part of https://github.com/osrf/homebrew-simulation/issues/2274. Cherry-picking forward to assist with rebuilding broken bottles.

Thanks to @traversaro for the patch!

Use rebase-and-merge.

[codecov[bot]]

Codecov Report

Merging #408 (c8a83da) into gz-transport12 (c958aec) will increase coverage by 0.13%. The diff coverage is 75.00%.

:exclamation: Current head c8a83da differs from pull request most recent head d00b4c9. Consider uploading reports for the commit d00b4c9 to get more accurate results

@@                Coverage Diff                 @@
##           gz-transport12     #408      +/-   ##
==================================================
+ Coverage           87.17%   87.31%   +0.13%     
==================================================
  Files                  60       60              
  Lines                5209     5211       +2     
==================================================
+ Hits                 4541     4550       +9     
+ Misses                668      661       -7     

Impacted Files	Coverage Δ
include/gz/transport/RepHandler.hh	85.36% <ø> (ø)
include/gz/transport/SubscriptionHandler.hh	84.90% <ø> (ø)
src/cmd/gz.cc	94.61% <75.00%> (-0.70%)	:arrow_down:

... and 2 files with indirect coverage changes

[scpeters]

attempting to fix a compiler warning in https://github.com/gazebosim/gz-transport/pull/408/commits/d00b4c948aecde733a9ae50f82c9ef4870dabebd

[scpeters]

attempting to fix a compiler warning in d00b4c9

coverage is slightly worse, but I'm not sure how to test the error case, so I'll just continue in order to get the fix merged