store test [nfc]: Replace old method name in a test group

This looks like it was meant to happen in 9201ae4.

Author: chrisbobbe

test/model/store_test.dart

@@ -31,7 +31,7 @@ import 'test_store.dart';
 void main() {
   TestZulipBinding.ensureInitialized();
 
-  group('GlobalStore.updateGlobalSettings', () {
+  group('GlobalStore update settings', () {
     test('smoke', () async {
       final globalStore = eg.globalStore();
       check(globalStore).settings.themeSetting.equals(null);