add missing `await`s (#144978)

This was uncovered as part of https://github.com/flutter/flutter/pull/144706.

packages/flutter/test/material/chip_test.dart

@@ -5131,7 +5131,7 @@ void main() {
     );
 
     // Delete button should be visible.
-    expectLater(find.byType(RawChip), matchesGoldenFile('raw_chip.disabled.delete_button.png'));
+    await expectLater(find.byType(RawChip), matchesGoldenFile('raw_chip.disabled.delete_button.png'));
   });
 
   testWidgets('Delete button tooltip is not shown on disabled RawChip', (WidgetTester tester) async {

packages/flutter/test/material/filter_chip_test.dart

@@ -1059,7 +1059,7 @@ void main() {
     );
 
     // Delete button should be visible.
-    expectLater(find.byType(RawChip), matchesGoldenFile('filter_chip.disabled.delete_button.png'));
+    await expectLater(find.byType(RawChip), matchesGoldenFile('filter_chip.disabled.delete_button.png'));
   });
 
   testWidgets('Delete button tooltip is not shown on disabled FilterChip', (WidgetTester tester) async {

packages/flutter/test/material/input_chip_test.dart

@@ -453,7 +453,7 @@ void main() {
     );
 
     // Delete button should be visible.
-    expectLater(find.byType(RawChip), matchesGoldenFile('input_chip.disabled.delete_button.png'));
+    await expectLater(find.byType(RawChip), matchesGoldenFile('input_chip.disabled.delete_button.png'));
   });
 
   testWidgets('Delete button tooltip is not shown on disabled InputChip', (WidgetTester tester) async {

packages/flutter/test/services/platform_views_test.dart

@@ -144,7 +144,7 @@ void main() {
         layoutDirection: TextDirection.ltr,
       );
       await controller.create(size: const Size(100.0, 100.0));
-      expectLater(
+      await expectLater(
         () {
           final AndroidViewController controller = PlatformViewsService.initAndroidView(
             id: 0,