autocomplete test: Add extra pump for new delay in upstream RawAutocomplete

The fixes to RawAutocomplete's options width in the Flutter framework:
  flutter/flutter#143249

introduces a one-frame delay, so this test will need an extra pump to
account for that.

Author: victorsanni

test/widgets/autocomplete_test.dart

@@ -224,6 +224,9 @@ void main() {
       await tester.enterText(composeInputFinder, 'hi :');
       await tester.enterText(composeInputFinder, 'hi :z');
       await tester.pump();
+      // Add an extra pump to account for any potential frame delays introduced
+      // by the post frame callback in RawAutocomplete's implementation.
+      await tester.pump();
       checkEmojiShown(expected: true, zzzOption);
       checkEmojiShown(expected: true, buzzingOption);
       checkEmojiShown(expected: true, zulipOption);