fix: return value from Part.delete() to support dry_run

Part.delete() was not returning the result from super().delete(),
causing dry_run=True to return None instead of the row count dict.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: dimitri-yatsenko

src/datajoint/user_tables.py

@@ -237,7 +237,7 @@ def delete(self, part_integrity: str = "enforce", **kwargs):
                 "or use part_integrity='ignore' to break integrity, "
                 "or part_integrity='cascade' to also delete master."
             )
-        super().delete(part_integrity=part_integrity, **kwargs)
+        return super().delete(part_integrity=part_integrity, **kwargs)
 
     def drop(self, part_integrity: str = "enforce", dry_run: bool = False):
         """