fix(db-mongodb): strip deleted from the config blocks from the result

[r1tsuu]

If you (using the MongoDB adapter) delete a block from the payload config, but still have some data with that block in the DB, you'd receive in the admin panel an error like:

Block with type "cta" was found in block data, but no block with that type is defined in the config for field with schema path pages.blocks

Now, we remove those "unknown" blocks at the DB adapter level.