fix: remove repeated docstring in _RewriteFiles and rely on documentation inheritance from method overriding

Author: qzyu999

pyiceberg/table/update/snapshot.py

@@ -720,11 +720,9 @@ def _get_entries(manifest: ManifestFile) -> list[ManifestEntry]:
             return []
 
     def _deleted_entries(self) -> list[ManifestEntry]:
-        """Check if we need to mark the files as deleted."""
         return self._cached_deleted_entries
 
     def _existing_manifests(self) -> list[ManifestFile]:
-        """To determine if there are any existing manifests."""
         return self._get_existing_manifests()