[test][cleanup] Remove test description above problem/spatialparams/main (in-code doc)

In many (system-)tests, we have a description of the scenario on top of the problem and sometimes running instructions. Such a description is only required for documented examples. In the test folder, it tends to easily become outdated or it's often wrong in the first place due to copy and paste. Running the test is already documented by CMakeLists.txt and should be done through CTest anyways. The description easily becomes outdated if the test is extended or changes.

This suggests removing any such "documentation" in the test folder.