Fix libsyntax update
Underscore is now one of keywords.
@@ -965,8 +965,7 @@ fn next_space(tok: &Token) -> SpaceState {
| Token::DotDotDot
| Token::DotDotEq
| Token::DotEq
- | Token::Question
- | Token::Underscore => SpaceState::Punctuation,
+ | Token::Question => SpaceState::Punctuation,
Token::ModSep
| Token::Pound
