Remove outdated STP tests

[nycrat]

Description of the task

These three tests use our old STP class which is removed now. The tests should be removed since they are not used, don't work, and aren't referred to anywhere in our code.

Acceptance criteria

• stp_referee_command_play_selection_test.cpp is gone
• stp_tactic_assignment_test.cpp is gone
• stp_test.cpp is gone

Blocked By

N/A