[JTC] Remove action_msg dependency (backport #1077)

[mergify]

We included a message header from action_msgs, but there is no need for that.
👀 ros-controls/control_msgs#115

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This is an automatic backport of pull request #1077 done by Mergify.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.09%. Comparing base (468e030) to head (044fc8c).

Additional details and impacted files

@@            Coverage Diff             @@
##           humble    #1080      +/-   ##
==========================================
- Coverage   72.15%   72.09%   -0.06%     
==========================================
  Files          40       40              
  Lines        3555     3555              
  Branches     1787     1788       +1     
==========================================
- Hits         2565     2563       -2     
- Misses        679      685       +6     
+ Partials      311      307       -4     

Flag	Coverage Δ
unittests	72.09% <ø> (-0.06%)	⬇️

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see 3 files with indirect coverage changes