Revert "Add temporary snippets/tasks folder for celery tasks to PYTHONPATH"
This reverts commit a3fe143766ac36acda9aa465bc61184d2a965c2e.
The task was migrated to swh-storage which is already on dev's
PYTHONPATH.
Related T557
Related b2be2336e98b6cb69b624e3fd3b071bcf2b99b6f
Related 183e60adac691bd15367b6b3517dc75dd072bf5b