fix UTF-32 valid_encoding?

* test/ruby/test_io_m17n.rb (TestIO_M17N#test_puts_widechar): do
  not use invalid codepoint.  [ruby-core:79966] [Bug #13292]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57817 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/ruby/test_io_m17n.rb

@@ -2237,7 +2237,7 @@ EOT
            w.binmode
            w.puts(0x010a.chr(Encoding::UTF_32BE))
            w.puts(0x010a.chr(Encoding::UTF_16BE))
-           w.puts(0x0a010000.chr(Encoding::UTF_32LE))
+           w.puts(0x0a01.chr(Encoding::UTF_32LE))
            w.puts(0x0a01.chr(Encoding::UTF_16LE))
            w.close
          end,
@@ -2245,7 +2245,7 @@ EOT
            r.binmode
            assert_equal("\x00\x00\x01\x0a\n", r.read(5), bug)
            assert_equal("\x01\x0a\n", r.read(3), bug)
-           assert_equal("\x00\x00\x01\x0a\n", r.read(5), bug)
+           assert_equal("\x01\x0a\x00\x00\n", r.read(5), bug)
            assert_equal("\x01\x0a\n", r.read(3), bug)
            assert_equal("", r.read, bug)
            r.close