Don't increment finished-subforms on comments.

[iamFIREcracker]

Currently, with lispindent taught to have a LIN of 2 for
DEFINE-GUESSER, indenting the following expression:

(cg:define-guesser apt-install
    ;; On Ubuntu, Bash suggests you to `apt install XXX` when the command
    ;; you just run was not found inside PATH.
    ;; This guesser looks looks for that suggestion.
    ("(sudo apt install [^ ]+)" (apt-cmd))
  (format NIL "~a" apt-cmd))

Would produce:

(cg:define-guesser apt-install
    ;; On Ubuntu, Bash suggests you to `apt install XXX` when the command
  ;; you just run was not found inside PATH.
  ;; This guesser looks looks for that suggestion.
  ("(sudo apt install [^ ]+)" (apt-cmd))
  (format NIL "~a" apt-cmd))

Note how only the first comment is properly indented. Well, this commit fixes it.

[iamFIREcracker]

@ds26gte - any chances this can be merged, or should I close this instead? I simply wanted to gauge your interest in this.