Fix search storage cleaning
Before moving storage cleaning to a parallel process in https://github.com/huggingface/dataset-viewer/issues/2718, there are some missing details and issues with the current process to fix:
- I removed `clean-directory` action from cache maintenance since we don't use this task anymore (we can add it later if needed)
- I found that clean_dir wasn't deleting the folder with a file that was last accessed time before X seconds ago. Index files change the last accessed time when being read by /search or /filter, but its parent folder didn't, so there wasn't a real cleaning when using the glob pattern; I also modified the test to cover this scenario.

Fix search storage cleaning: Before moving storage cleaning to a parallel process in https://github.com/huggingface/dataset-viewer/issues/2718, there are some missing details and issues with the current process to fix:
- I removed `clean-directory` action from cache maintenance since we don't use this task anymore (we can add it later if needed)
- I found that clean_dir wasn't deleting the folder with a file that was last accessed time before X seconds ago. Index files change the last accessed time when being read by /search or /filter, but its parent folder didn't, so there wasn't a real cleaning when using the glob pattern; I also modified the test to cover this scenario.
