Fix typo in list append operator in pcre-light-using code.

Text/Highlighting/Kate/Common.hs:187:25:
    No instance for (Num [PCREOption]) arising from a use of `+'
    Possible fix: add an instance declaration for (Num [PCREOption])
    In the expression:
      [anchored] + [caseless | not (synStCaseSensitive st)]
    In an equation for `opts':
        opts = [anchored] + [caseless | not (synStCaseSensitive st)]
    In the expression:
      do { st <- getState;
           let opts = ... + ...;
           return $ compile ('.' : convertOctal regexpStr) opts }