Remove deleted collection from crawling defaults

[tw4l]

Fixes #3176

Removes deleted collection from Organization.crawlingDefaults.dedupeCollId if the collection was set as the dedupe coll source

Testing

1. Create a dedupe collection
2. Set it as the org crawling default dedupe source
3. Delete the collection
4. Verify that the collection is no longer set in org crawling defaults

[SuaYoo]

Tested in the UI, looks good. Pushed one frontend change to reload crawling defaults after a collection is deleted 0c19043 (cc @emma-sg )