Remove tabs from BNF comments

Minor cleanup on the BNF comments - get rid of tabs and align them

lib/oxttl/src/lexer.rs

@@ -240,7 +240,6 @@ impl N3Lexer {
     ) -> Option<(usize, Result<N3Token<'a>, TokenRecognizerError>)> {
         // [139s]  PNAME_NS   ::=  PN_PREFIX? ':'
         // [140s]  PNAME_LN   ::=  PNAME_NS PN_LOCAL
-
         // [167s]  PN_PREFIX  ::=  PN_CHARS_BASE ((PN_CHARS | '.')* PN_CHARS)?
         let mut i = 0;
         loop {