Increase timeout to avoid occasional timeout exceeded on macos bots (#2544)

Author: jcollins-g

test/mustachio/builder_test.dart

@@ -222,7 +222,7 @@ import 'package:mustachio/annotations.dart';
     expect(renderersLibrary.getTopLevelFunction('renderBar'), isNotNull);
     expect(renderersLibrary.getType('_Renderer_Foo'), isNotNull);
     expect(renderersLibrary.getType('_Renderer_Bar'), isNotNull);
-  });
+  }, timeout: Timeout.factor(2));
 
   group('builds a renderer class for a generic type', () {
     String generatedContent;