do fetchSiteName func to useEffect

src/client/js/components/Admin/SlackIntegration/CustomBotWithoutProxySettings.jsx

@@ -40,6 +40,7 @@ const CustomBotWithoutProxySettings = (props) => {
   };
 
   useEffect(() => {
+    fetchSiteName();
     setSlackWSNameInWithoutProxy(null);
     if (props.isSetupSlackBot) {
       fetchSlackWorkSpaceName();