Prepare for 4.9.0 release

[nkoenig]

Signed-off-by: Nate Koenig [email protected]

🎈 Release

Preparation for 4.9.0 release.

Comparison to 4.8.0: ignition-gazebo4_4.8.0...ign-gazebo4

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 ignition-release (as needed):

Note to maintainers: Remember to use Squash-Merge

[codecov]

Codecov Report

Merging #829 (97b7973) into ign-gazebo4 (6619271) will increase coverage by 0.03%.
The diff coverage is n/a.

❗ Current head 97b7973 differs from pull request most recent head 04a1a3f. Consider uploading reports for the commit 04a1a3f to get more accurate results

@@               Coverage Diff               @@
##           ign-gazebo4     #829      +/-   ##
===============================================
+ Coverage        65.73%   65.77%   +0.03%     
===============================================
  Files              241      241              
  Lines            17839    17839              
===============================================
+ Hits             11727    11733       +6     
+ Misses            6112     6106       -6     

Impacted Files	Coverage Δ
src/SimulationRunner.cc	94.01% <0.00%> (+1.05%)	⬆️

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[scpeters]

wiped workspace and retrying homebrew build