[es8] Remove syntactic tail calls support.

test/message/syntactic-tail-call-without-return.js

Index: test/message/syntactic-tail-call-without-return.js
diff --git a/test/message/syntactic-tail-call-without-return.js b/test/message/syntactic-tail-call-without-return.js
deleted file mode 100644
index 130f67dafc1c638de8efad556f9e4c9ba6a587c0..0000000000000000000000000000000000000000
--- a/test/message/syntactic-tail-call-without-return.js
+++ /dev/null
@@ -1,14 +0,0 @@
-// Copyright 2016 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: --harmony-explicit-tailcalls
-"use strict";
-
-function f() {
-  return 1;
-}
-
-function g() {
-  var x =  continue  f()  ;
-}