Remove redundant and indirect tests

A number of tests for string literals assert the restriction on
LegacyOctalEscapeSequence in strict mode code and differ only in the
escape sequence under test. Although each is valid, none of the escape
sequences are sufficiently distinct from the test
'legacy-octal-escape-sequence-stricts.js' to warrant their inclusion in
the test suite. Because that test's use of literal code makes it
consumable by parsers and because that test includes much more thorough
documentation, it should be preferred.

Summary of LegacyOctalEscapeSequences under test in the removed files:

    test/language/literals/string/7.8.4-10-s.js: eval('var x = " \\10 ";');
    test/language/literals/string/7.8.4-11-s.js: eval('var x = "\\16";');
    test/language/literals/string/7.8.4-12-s.js: eval('var x = "\\17";');
    test/language/literals/string/7.8.4-13-s.js: eval('var x = "\\30";');
    test/language/literals/string/7.8.4-14-s.js: eval('var x = "\\31";');
    test/language/literals/string/7.8.4-15-s.js: eval('var x = "\\37";');
    test/language/literals/string/7.8.4-16-s.js: eval('var x = "\\400";');
    test/language/literals/string/7.8.4-17-s.js: eval('var x = "\\411";');
    test/language/literals/string/7.8.4-18-s.js: eval('var x = "\\43a";');
    test/language/literals/string/7.8.4-19-s.js: eval('var x = "\\463";');
    test/language/literals/string/7.8.4-2-s.js:  eval('var x = "\\1";');
    test/language/literals/string/7.8.4-20-s.js: eval('var x = "\\474";');
    test/language/literals/string/7.8.4-21-s.js: eval('var x = "\\77";');
    test/language/literals/string/7.8.4-22-s.js: eval('var x = "\\777";');
    test/language/literals/string/7.8.4-23-s.js: eval('var x = "\\000";');
    test/language/literals/string/7.8.4-24-s.js: eval('var x = "\\001";');
    test/language/literals/string/7.8.4-25-s.js: eval('var x = "\\106";');
    test/language/literals/string/7.8.4-26-s.js: eval('var x = "\\207";');
    test/language/literals/string/7.8.4-27-s.js: eval('var x = "\\377";');
    test/language/literals/string/7.8.4-28-s.js: eval('var x = "\\376";');
    test/language/literals/string/7.8.4-29-s.js: eval('var x = "\\3760";');
    test/language/literals/string/7.8.4-3-s.js:  eval('var x = "a\\4";');
    test/language/literals/string/7.8.4-32-s.js: eval('var x = "\\1\\1";');
    test/language/literals/string/7.8.4-33-s.js: eval('var x = "\\1\\2\\7";');
    test/language/literals/string/7.8.4-4-s.js:  eval('var x = "z\\7";');
    test/language/literals/string/7.8.4-5-s.js:  eval('var x = "\\00a";');
    test/language/literals/string/7.8.4-6-s.js:  eval('var x = "\\01z";');
    test/language/literals/string/7.8.4-7-s.js:  eval('var x = "a\\03z";');
    test/language/literals/string/7.8.4-8-s.js:  eval('var x = " \\06";');