[strong] Remove all remainders of strong mode

test/mjsunit/strong/delete.js

Index: test/mjsunit/strong/delete.js
diff --git a/test/mjsunit/strong/delete.js b/test/mjsunit/strong/delete.js
deleted file mode 100644
index 349af0bf3905f16efc093e805289ce05ca7d2a08..0000000000000000000000000000000000000000
--- a/test/mjsunit/strong/delete.js
+++ /dev/null
@@ -1,11 +0,0 @@
-// Copyright 2015 the V8 project authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-// Flags: --strong-mode
-
-(function NoDelete() {
-  const o = {a: 0};
-  assertThrows("'use strong'; delete o.a", SyntaxError);
-  assertThrows("'use strong'; delete o", SyntaxError);
-})();