Remove position controllers from Hybrid Planning CMake

[vatanaksoytezer]

Humble and Rolling buildfarm has been failing with the following error:

14:25:06 CMake Error at CMakeLists.txt:15 (find_package):
14:25:06   By not providing "Findposition_controllers.cmake" in CMAKE_MODULE_PATH this
14:25:06   project has asked CMake to find a package configuration file provided by
14:25:06   "position_controllers", but CMake did not find one.
14:25:06 
14:25:06   Could not find a package configuration file provided by
14:25:06   "position_controllers" with any of the following names:
14:25:06 
14:25:06     position_controllersConfig.cmake
14:25:06     position_controllers-config.cmake
14:25:06 
14:25:06   Add the installation prefix of "position_controllers" to CMAKE_PREFIX_PATH
14:25:06   or set "position_controllers_DIR" to a directory containing one of the
14:25:06   above files.  If "position_controllers" provides a separate development
14:25:06   package or SDK, be sure it has been installed.
14:25:06 

Although position_controllers is only a run depend, it has been listed in the cmake. This PR removes it in an attempt to fix the buildfarm

[vatanaksoytezer]

We need a new release after this to get the buildfarm passing again

[codecov]

Codecov Report

Merging #1285 (fda0780) into main (9bbe46a) will increase coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1285      +/-   ##
==========================================
+ Coverage   61.45%   61.47%   +0.02%     
==========================================
  Files         274      274              
  Lines       24940    24940              
==========================================
+ Hits        15325    15329       +4     
+ Misses       9615     9611       -4     

Impacted Files	Coverage Δ
...nning_scene_monitor/src/planning_scene_monitor.cpp	45.73% <0.00%> (+0.44%)	⬆️

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[AndyZe]

I wish you would have left a TODO to put it back. It does belong there. But no big deal.