Fix Temp File Size Unit Test

[Satrat]

1. Adding tmp_path_retention_policy = "none" to pyproject.toml so that pytest deletes its temp files after every session, freeing up disk space.
2. Because pytest takes care of deleting its own files, we can exclude them from the file size check in conftest.py

Testing

run make test TARGETS=transformers

Old Behavior

check_for_created_files() fails with error:

Failed: failed on teardown with "AssertionError: 2506.184633255005 megabytes of temp files created
 in temp directory during pytest run. 

New Behavior

tests pass without errors

[dbogunowicz]

@dbarbuzzi pinging you, so that you can rerun tests after this lands :)