Remove the forked controller manager node after next release and sync

[eholum-nasa]

As in #9.

Another safety change went into the upstream for handling runtime exceptions when shutting down the node: ros-controls/ros2_control#2963

This was added to the forked controller manager node in https://github.com/ros-controls/mujoco_ros2_control/pull/66/files#diff-7de47392cb4e3d4f3ea3d2fe2e9196aa794b2b76bdb42f7f6b492a233dc8028dR170.

Once the upstream is released, we should be able to remove the node. Opening this ticket so that we remember to do that.