fix: fix flashing error dialog in the create workspace page (coder#18180)

This PR which updated react-query to 5.77.0 introduced an issue on the
create workspace page where the error dialog would be briefly displayed
while the page is loading. coder#18039

The issue is that there is a moment when `optOutQuery.isLoading` is
false and `optOutQuery.data` is undefined causing the ErrorAlert to
display.

Author: jaaydenh

site/src/pages/CreateWorkspacePage/CreateWorkspaceExperimentRouter.tsx

@@ -44,11 +44,11 @@ const CreateWorkspaceExperimentRouter: FC = () => {
 	});
 
 	if (dynamicParametersEnabled) {
-		if (optOutQuery.isLoading) {
-			return <Loader />;
+		if (optOutQuery.isError) {
+			return <ErrorAlert error={optOutQuery.error} />;
 		}
 		if (!optOutQuery.data) {
-			return <ErrorAlert error={optOutQuery.error} />;
+			return <Loader />;
 		}
 
 		const toggleOptedOut = () => {