Recently added pipelines tests should be marked as slow
## 🐛 Bug

Starting today, when running tests, some very large files are downloaded even though I don't enable RUN_SLOW=true.

Some tests in pipelines_test.py should be marked with `@slow` so they don't run unless RUN_SLOW=True.
This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.
