Fix light_control example and update tutorial

[iche033]

🦟 Bug fix

gazebosim/gazebo_test_cases#285

Summary

Running the example had no effect because the light intensity defaults to 0 if not set. Updated the example to set the light intensity values and made some minor clarifications to the tutorial

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 #2149 (26a77db) into gz-sim8 (294fddc) will not change coverage.
Report is 1 commits behind head on gz-sim8.
The diff coverage is n/a.

❗ Current head 26a77db differs from pull request most recent head 93151c1. Consider uploading reports for the commit 93151c1 to get more accurate results

@@           Coverage Diff            @@
##           gz-sim8    #2149   +/-   ##
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  Coverage    65.47%   65.47%           
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  Files          323      323           
  Lines        30704    30704           
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  Hits         20102    20102           
  Misses       10602    10602