Prepare for 7.3.0 Release

[azeey]

🎈 Release

Preparation for 7.3.0 release.

Comparison to 7.2.0: gz-math7_7.2.0...gz-math7

Needed by gazebosim/sdformat#1299.

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 #552 (36039e0) into gz-math7 (3d9cf33) will not change coverage.
The diff coverage is n/a.

❗ Current head 36039e0 differs from pull request most recent head 1237176. Consider uploading reports for the commit 1237176 to get more accurate results

@@            Coverage Diff            @@
##           gz-math7     #552   +/-   ##
=========================================
  Coverage     94.16%   94.16%           
=========================================
  Files           145      145           
  Lines          9774     9774           
=========================================
  Hits           9204     9204           
  Misses          570      570