Delete emptied ShouldGenerateCandidates files (#5050)

Summary:
Pull Request resolved: #5050

Delete the emptied should_generate_candidates.py and its test file. These files
were emptied in the previous diff after removing all references.

Reviewed By: bernardbeckerman

Differential Revision: D96929994

fbshipit-source-id: fef6563c434cdc9eda3a017188f20cc757b8a9e1

Author: shrutipatel31