Remove gazebo scene viewer example

[iche033]

🦟 Bug fix

gazebosim/gazebo_test_cases#693

Summary

Remove example as it no longer runs. Gazebo-classic (gazebo11) depends on different versions of gz that causes issues at run time. It also does not work on macOS.

Checklist

• Signed all commits for DCO
• Added tests
• 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.

[codecov]

Codecov Report

Merging #915 (3e2dabb) into gz-rendering8 (5655566) will not change coverage.
The diff coverage is n/a.

❗ Current head 3e2dabb differs from pull request most recent head f92e21c. Consider uploading reports for the commit f92e21c to get more accurate results

@@              Coverage Diff               @@
##           gz-rendering8     #915   +/-   ##
==============================================
  Coverage          75.16%   75.16%           
==============================================
  Files                177      177           
  Lines              16849    16849           
==============================================
  Hits               12665    12665           
  Misses              4184     4184