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.
Co-authored-by: Dan Ribbens <dan.ribbens@gmail.com>
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