Update Migration guide

[iche033]

🎉 New feature

Summary

Update Migration update with info on deprecated function, see https://github.com/ignitionrobotics/ign-rendering/pull/534/files#r781598375

Checklist

• Signed all commits for DCO
• Added tests
• Added example and/or tutorial
• Updated documentation (as needed)
• Updated migration guide (as needed)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

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 #538 (47560de) into main (78baf76) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #538   +/-   ##
=======================================
  Coverage   53.39%   53.39%           
=======================================
  Files         211      211           
  Lines       20818    20818           
=======================================
  Hits        11115    11115           
  Misses       9703     9703           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 78baf76...47560de. Read the comment docs.