Add missing copyright on test cases.

pkg/front_end/testcases/void-methods.dart.strong.expect

Index: pkg/front_end/testcases/void-methods.dart.strong.expect
diff --git a/pkg/front_end/testcases/void-methods.dart.strong.expect b/pkg/front_end/testcases/void-methods.dart.strong.expect
deleted file mode 100644
index 683d3ae30cc2d06d96920f74bf6c4e98157d3be1..0000000000000000000000000000000000000000
--- a/pkg/front_end/testcases/void-methods.dart.strong.expect
+++ /dev/null
@@ -1,21 +0,0 @@
-library;
-import self as self;
-import "dart:core" as core;
-
-class Foo extends core::Object {
-  field core::List<dynamic> list = <dynamic>[1, 2, 3];
-  default constructor •() → void
-    : super core::Object::•()
-    ;
-  set first(dynamic x) → void
-    this.list.[]=(0, x);
-  operator []=(dynamic x, dynamic y) → void
-    this.list.[]=(x, y);
-  method clear() → void
-    return this.{self::Foo::list}.{core::List::clear}();
-}
-static method main() → dynamic {
-  new self::Foo::•().{self::Foo::first} = 4;
-  new self::Foo::•().{self::Foo::[]=}(3, 4);
-  new self::Foo::•().{self::Foo::clear}();
-}