DROP CAST removes a previously defined cast.
To be able to drop a cast, you must own the source or the target data type. These are the same privileges that are required to create a cast.
Do not throw an error if the cast does not exist. A notice is issued in this case.
The name of the source data type of the cast.
The name of the target data type of the cast.
These key words do not have any effect, since there are no dependencies on casts.