Fix thrust cmd topic in underwater tutorial

[iche033]

🦟 Bug fix

Summary

Fixes thrust cmd topic name as found in gazebosim/gazebo_test_cases#393

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 #2120 (f052167) into gz-sim7 (5ebf860) will decrease coverage by 0.01%.
Report is 1 commits behind head on gz-sim7.
The diff coverage is n/a.

❗ Current head f052167 differs from pull request most recent head 54f8946. Consider uploading reports for the commit 54f8946 to get more accurate results

@@             Coverage Diff             @@
##           gz-sim7    #2120      +/-   ##
===========================================
- Coverage    65.01%   65.01%   -0.01%     
===========================================
  Files          356      356              
  Lines        28929    28929              
===========================================
- Hits         18808    18807       -1     
- Misses       10121    10122       +1     

see 1 file with indirect coverage changes