Remove erroneous test

This test is technically valid because it does trigger a SyntaxError in
conforming runtimes. However, it was authored and documented to test
LegacyOctalEscapeSequence, but due to an apparent typo, it actually
demonstrates an unrelated parsing error.

Because 'legacy-octal-escape-sequence-stricts.js' sufficiently tests the
restriction on LegacyOctalEscapeSequence, remove this test rather than
correct it.

test/language/literals/string/7.8.4-31-s.js

-// Copyright (c) 2012 Ecma International.  All rights reserved.
-// This code is governed by the BSD license found in the LICENSE file.
-
-/*---
-es5id: 7.8.4-31-s
-description: An OctalEscapeSequence is not allowed in a String under Strict Mode
-flags: [onlyStrict]
----*/
-
-
-assert.throws(SyntaxError, function() {
-    eval('var x = "\\" + "1";');
-});