Update underwater_vehicles.md

[ahcorde]

🦟 Documentation fix

Fixes gazebosim/gazebo_test_cases#394

Summary

Fixed topic name

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 #2128 (41e918f) into gz-sim8 (923ccee) will decrease coverage by 0.01%.
Report is 4 commits behind head on gz-sim8.
The diff coverage is n/a.

❗ Current head 41e918f differs from pull request most recent head 61e4af5. Consider uploading reports for the commit 61e4af5 to get more accurate results

@@             Coverage Diff             @@
##           gz-sim8    #2128      +/-   ##
===========================================
- Coverage    65.45%   65.45%   -0.01%     
===========================================
  Files          323      323              
  Lines        30704    30704              
===========================================
- Hits         20097    20096       -1     
- Misses       10607    10608       +1     

see 1 file with indirect coverage changes

[Voldivh]

Besides the comment from @iche033 , LGTM

[Voldivh]

LGTM!