[JTC] Update requirements of state interfaces (backport #798)

[mergify]

This is an automatic backport of pull request #798 done by Mergify.
Cherry-pick of c831b6c has failed:

On branch mergify/bp/humble/pr-798
Your branch is up to date with 'origin/humble'.

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Changes to be committed:
	modified:   joint_trajectory_controller/include/joint_trajectory_controller/validate_jtc_parameters.hpp

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   joint_trajectory_controller/doc/userdoc.rst

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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[christophfroehlich]

included in #801