Fix buggy sizeof

A sizeof on a pointer on a 64 bit machine is 8 bytes whereas
Entry::old_name is a 64 byte array of characters. There was most likely
no fallout since the string would start with NUL bytes, but best to fix
nonetheless.

Signed-off-by: Tristan Partin <tristan@neon.tech>

pgxn/neon/control_plane_connector.c

@@ -767,7 +767,7 @@ HandleDropRole(DropRoleStmt *stmt)
 		entry->type = Op_Delete;
 		entry->password = NULL;
 		if (!found)
-			memset(entry->old_name, 0, sizeof(entry));
+			memset(entry->old_name, 0, sizeof(entry->old_name));
 	}
 }