Update or delete language tests using obsolete interfaces or default factory

tests/language/cyclic_type_variable_test.dart

Index: tests/language/cyclic_type_variable_test.dart
===================================================================
--- tests/language/cyclic_type_variable_test.dart	(revision 15648)
+++ tests/language/cyclic_type_variable_test.dart	(working copy)
@@ -8,24 +8,24 @@
 
 class Derived extends Base<Derived> {}  // legal
 
-typedef void funcType<T 
+typedef void funcType<T
 extends T /// 01: static type warning
 >(T arg);
 
 class DerivedFunc extends Base<funcType<DerivedFunc>> { }
 
 
-interface A<S 
+abstract class A<S
 extends S /// 02: static type warning
 > {
   S field;
 }
 
-interface B<U extends Base<U>> { // legal
+abstract class B<U extends Base<U>> { // legal
   U field;
 }
 
-class C1<V 
+class C1<V
 extends V  /// 03: static type warning
 > {
   V field;