Remove gripper_controllers dependency

[fmauch]

The package got removed upstream in ros-controls/ros2_controllers#1652. Find_packageing this on Kilted or Rolling will lead to errors from the next sync on.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 46.23%. Comparing base (3758a0f) to head (95d02a3).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3474      +/-   ##
==========================================
- Coverage   46.23%   46.23%   -0.00%     
==========================================
  Files         718      718              
  Lines       62677    62683       +6     
  Branches     7583     7588       +5     
==========================================
+ Hits        28975    28976       +1     
- Misses      33535    33540       +5     
  Partials      167      167              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[urfeex]

Note: While the buildfarm for Kilted looks fine, it actually leaves an uninstallable package, as the gripper_controllers exec dependency cannot be found:

$ sudo apt-get install -y ros-kilted-moveit-servo
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 ros-kilted-moveit-servo : Depends: ros-kilted-gripper-controllers but it is not installable
E: Unable to correct problems, you have held broken packages.