Remove _set_document

Author: NoahStapp

bson/errors.py

@@ -44,9 +44,6 @@ def document(self) -> Any:
         ..versionadded:: 4.16"""
         return self._document
 
-    def _set_document(self, value: Any) -> None:
-        self._document = value
-
 
 class InvalidId(BSONError):
     """Raised when trying to create an ObjectId from invalid data."""