Move test infer_use_of_void to inference_new

pkg/front_end/testcases/inference/infer_use_of_void_local.dart

 // Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /*@testedFeatures=inference*/
 library test;
 
-class B {
-  void f() {}
+void f() {}
+
+void g() {
+  var /*@type=void*/ x = f();
 }
 
-class C extends B {
-  /*@topType=void*/ f() {}
-}
-
-var /*@topType=dynamic*/ x =
-    new C(). /*info:USE_OF_VOID_RESULT*/ /*@target=C::f*/ f();
-
-main() {
-  x;
-}
+main() {}