Update to latest pygments

Ran `rake vendor:update`.

There is one failing test that seems like a legitimate failure. The test was added in d6a8f2af7d20eb71184d6bd7ca60e00501146e88, which appears to be testing pipes and not necessarily the expected output.

```
[26/48] PygmentsHighlightTest#test_highlight_works_with_single_character_input = 0.01 s                    
  1) Error:
test_highlight_works_with_single_character_input(PygmentsHighlightTest):
MentosError: Traceback (most recent call last):
  File "/Users/brandon/github/pygments.rb/lib/pygments/mentos.py", line 303, in start
    res = self.get_data(method, lexer, args, kwargs, text)
  File "/Users/brandon/github/pygments.rb/lib/pygments/mentos.py", line 171, in get_data
    res = self.highlight_text(text, lexer, formatter_name, args, _convert_keys(opts))
  File "/Users/brandon/github/pygments.rb/lib/pygments/mentos.py", line 122, in highlight_text
    lexer = self.return_lexer(lexer, args, kwargs, code)
  File "/Users/brandon/github/pygments.rb/lib/pygments/mentos.py", line 102, in return_lexer
    return lexers.guess_lexer(code, **inputs)
  File "/Users/brandon/github/pygments.rb/vendor/pygments-main/pygments/lexers/__init__.py", line 242, in guess_lexer
    raise ClassNotFound('no lexer matching the text found')
ClassNotFound: no lexer matching the text found
```