Fix undefined variable in previous commit (bug#73900)

I somehow thought allow-auto-fill is a global variable that's
used by cc.  But it's not.  It's just a function param used by
c-indent-new-comment-line.

* lisp/progmodes/c-ts-common.el:
(c-ts-common-comment-indent-new-line): Remove reference to
allow-auto-fill.

lisp/progmodes/c-ts-common.el

@@ -307,7 +307,7 @@ and /* */ comments.  SOFT works the same as in
 	   (delete-horizontal-space)
 	   (if soft
 	       (insert-and-inherit ?\n)
-	     (newline (if allow-auto-fill nil 1))))))
+	     (newline 1)))))
     (cond
      ;; Line starts with //, or ///, or ////...
      ;; Or //! (used in rust).