Remove unnecessary `mockdata` parameters

[michplunkett]

Fixes issue

https://github.com/lucyparsons/OpenOversight/issues/1125

Description of Changes

Removed the mockdata parameter from test functions that don't require it.

Tests and Linting

• [x] This branch is up-to-date with the develop branch.
• [x] pytest passes on my local development environment.
• [x] pre-commit passes on my local development environment.

[michplunkett]

@abandoned-prototype, we still use mockdata in other tests throughout various files (test_descriptions.py, test_image_tagging.py, test_functional, test_models, etc.) and , so we can't get rid of it quite yet. To remove those lines, we'd need to do some general test restructuring that would go beyond this simple pruning.