Use tf prefix properly (backport #688)

[mergify]

This is an automatic backport of pull request #688 done by Mergify.
Cherry-pick of 7cda9c1 has failed:

On branch mergify/bp/humble/pr-688
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	modified:   Universal_Robots_ROS2_Driver-not-released.humble.repos

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[fmauch]

I tested locally with a modified controllers.yaml and it seems to be working fine with a tf_prefix on humble.