update suggestion element return type to have type param

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

Index: pkg/analysis_server/test/services/completion/prefixed_element_contributor_test.dart
diff --git a/pkg/analysis_server/test/services/completion/prefixed_element_contributor_test.dart b/pkg/analysis_server/test/services/completion/prefixed_element_contributor_test.dart
index eb6826ee0475e46ead9a9eb4425604fb078bd994..777886933a482887e1b6d6dea0e20420dff5f430 100644
--- a/pkg/analysis_server/test/services/completion/prefixed_element_contributor_test.dart
+++ b/pkg/analysis_server/test/services/completion/prefixed_element_contributor_test.dart
@@ -238,7 +238,7 @@ void f(C<int> c) {
     addTestSource('import "dart:async" deferred as bar; foo() {bar.^}');
     return computeFull((bool result) {
       assertSuggestClass('Future');
-      assertSuggestFunction('loadLibrary', 'void');
+      assertSuggestFunction('loadLibrary', 'Future<dynamic>');
     });
   }