Fix hints and clean-up obsolete comment syntax (TBR)

pkg/analysis_server/test/services/completion/dart/completion_contributor_util.dart

Index: pkg/analysis_server/test/services/completion/dart/completion_contributor_util.dart
diff --git a/pkg/analysis_server/test/services/completion/dart/completion_contributor_util.dart b/pkg/analysis_server/test/services/completion/dart/completion_contributor_util.dart
index 736a391780ab881449e067a1c9277ecfa9d71b4a..b5da3558f9e79c761dfac249922150647757b493 100644
--- a/pkg/analysis_server/test/services/completion/dart/completion_contributor_util.dart
+++ b/pkg/analysis_server/test/services/completion/dart/completion_contributor_util.dart
@@ -564,8 +564,7 @@ abstract class DartCompletionContributorTest extends AbstractContextTest {
     return cs;
   }
 
-  Future/*<E>*/ performAnalysis/*<E>*/(
-      int times, Completer/*<E>*/ completer) async {
+  Future<E> performAnalysis<E>(int times, Completer<E> completer) async {
     if (completer.isCompleted) {
       return completer.future;
     }