sway/config.c: Change to the useful free_cmd_results helper method

sway/config.c

@@ -536,8 +536,7 @@ bool read_config(FILE *file, struct sway_config *config) {
 		default:;
 		}
 		free(line);
-		free(res->input);
-		free(res);
+		free_cmd_results(res);
 	}
 
 	return success;