Fix enable/reenable of swagger UI endpoint

docs/rest-api.md

@@ -266,7 +266,7 @@ whitelist
 
 ## OpenAPI interface
 
-To enable the builtin openAPI interface, specify `"enable_openapi": true` in the api_server configuration.
+To enable the builtin openAPI interface (Swagger UI), specify `"enable_openapi": true` in the api_server configuration.
 This will enable the Swagger UI at the `/docs` endpoint. By default, that's running at http://localhost:8080/docs/ - but it'll depend on your settings.
 
 ## Advanced API usage using JWT tokens

freqtrade/rpc/api_server/webserver.py

@@ -30,8 +30,7 @@ class ApiServer(RPCHandler):
         api_config = self._config['api_server']
 
         self.app = FastAPI(title="Freqtrade API",
-                           openapi_url='openapi.json' if api_config.get(
-                               'enable_openapi', False) else None,
+                           docs_url='/docs' if api_config.get('enable_openapi', False) else None,
                            redoc_url=None,
                            )
         self.configure_app(self.app, self._config)