Indicate that Gazebo Fortress is recommended for ROS 2 Humble and Iron users

[azeey]

🦟 Bug fix

Summary

The "Recommended" label on Harmonic can be confusing since we don't actually recommend it for use with ROS 2 Humble or Iron.

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.

cc @knmcguire, @Ryanf55

[Ryanf55]

Nice, this clears up the confusion for me.

[knmcguire]

Great! That will improve things. Thanks @azeey !