Fix controller dependencies (backport #837)

[mergify]

We only use JTC or forward_command_controller for the demos, the specializations got removed with ros-controls/ros2_controllers#2016

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This is an automatic backport of pull request #837 done by Mergify.

[mergify]

Cherry-pick of 54addf2 has failed:

On branch mergify/bp/humble/pr-837
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	both modified:   gz_ros2_control_demos/package.xml

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