Alphabetize examples

[chapulina]

Summary

They're already alphabetized on main, so doing it on math6 too helps with forward-ports and reducing the diff.

https://github.com/gazebosim/gz-math/blob/main/examples/CMakeLists.txt#L9-L70

Checklist

• Signed all commits for DCO
• Added tests
• Added example and/or tutorial
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• 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.

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[codecov]

Codecov Report

Merging #457 (20e86b0) into ign-math6 (534f73a) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           ign-math6     #457   +/-   ##
==========================================
  Coverage      99.68%   99.68%           
==========================================
  Files             73       73           
  Lines           6901     6901           
==========================================
  Hits            6879     6879           
  Misses            22       22           

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