Remove unneeded parentheses from Python file (#12968)

airflow/cli/cli_parser.py

@@ -178,7 +178,7 @@ ARG_OUTPUT = Arg(
         "-o",
         "--output",
     ),
-    help=("Output format. Allowed values: json, yaml, table (default: table)"),
+    help="Output format. Allowed values: json, yaml, table (default: table)",
     metavar="(table, json, yaml)",
     choices=("table", "json", "yaml"),
     default="table",