fix: fix arg type

src/gradio_app.py

@@ -85,7 +85,7 @@ if __name__ == "__main__":
         description="Holocron image classification demo", formatter_class=ArgumentDefaultsHelpFormatter
     )
     parser.add_argument("--repo", type=str, default="frgfm/rexnet1_0x", help="HF Hub repo to use")
-    parser.add_argument("--port", type=int | None, default=None, help="Port on which the webserver will be run")
+    parser.add_argument("--port", type=int, default=None, help="Port on which the webserver will be run")
     args = parser.parse_args()
 
     main(args)