Prepare for 12.2.1 Release

[azeey]

🎈 Release

Preparation for 12.2.1 release.

Comparison to 12.2.0: gz-transport12_12.2.0...gz-transport12

Checklist

• Asked team if this is a good time for a release
• There are no changes to be ported from the previous major version
• No PRs targeted at this major version are close to getting in
• Bumped minor for new features, patch for bug fixes
• Updated changelog
• Updated migration guide (as needed)
• Link to PR updating dependency versions in appropriate repository in gazebo-release (as needed):

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[codecov]

Codecov Report

Merging #444 (5e2423d) into gz-transport12 (685ad65) will decrease coverage by 0.04%.
The diff coverage is n/a.

❗ Current head 5e2423d differs from pull request most recent head 57fa064. Consider uploading reports for the commit 57fa064 to get more accurate results

@@                Coverage Diff                 @@
##           gz-transport12     #444      +/-   ##
==================================================
- Coverage           87.33%   87.29%   -0.04%     
==================================================
  Files                  60       60              
  Lines                5211     5211              
==================================================
- Hits                 4551     4549       -2     
- Misses                660      662       +2     

see 1 file with indirect coverage changes