So you deleted some content type fields. Awesome!
Now you have a bunch of fields in your database that look like:
field_deleted_data_1 field_deleted_data_2 field_deleted_revision_1 field_deleted_revision_2
Drupal keeps them around, and even updates them, just because it can 🙂
How do you actually delete these fields/tables?
First, you need to modify field_config and field_config_instance and remove references to these fields first.
delete from field_config where deleted = 1; delete from field_config_instance where deleted = 1;
Next, drop the field_deleted_* tables.
That’s it. You actually deleted the fields now.