Prepare for 13.1.0 Release

[azeey]

🎈 Release

Preparation for 13.1.0 release.

Comparison to 13.0.0: https://github.com/gazebosim/gz-transport/compare/gz-transport13_13.0.0...gz-transport13

Needed by <PR(s)>

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[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 87.70%. Comparing base (eac2e69) to head (2ea16bc). Report is 4 commits behind head on gz-transport13.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## gz-transport13 #482 +/- ## ================================================== + Coverage 87.69% 87.70% +0.01% ================================================== Files 59 59 Lines 5704 5710 +6 ================================================== + Hits 5002 5008 +6 Misses 702 702 ```

:umbrella: View full report in Codecov by Sentry.
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