dir.c: drop unused "untracked" from treat_path_fast()

We don't use the untracked_cache_dir parameter that is passed in, but
instead look at the untracked_cache_dir inside the cached_dir struct we
are passed. It's been this way since the introduction of
treat_path_fast() in 91a2288b5f (untracked cache: record/validate dir
mtime and reuse cached output, 2015-03-08).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

dir.c

@@ -2105,7 +2105,6 @@ static int resolve_dtype(int dtype, struct index_state *istate,
 }
 
 static enum path_treatment treat_path_fast(struct dir_struct *dir,
-					   struct untracked_cache_dir *untracked,
 					   struct cached_dir *cdir,
 					   struct index_state *istate,
 					   struct strbuf *path,
@@ -2153,7 +2152,7 @@ static enum path_treatment treat_path(struct dir_struct *dir,
 	int has_path_in_index, dtype, excluded;
 
 	if (!cdir->d_name)
-		return treat_path_fast(dir, untracked, cdir, istate, path,
+		return treat_path_fast(dir, cdir, istate, path,
 				       baselen, pathspec);
 	if (is_dot_or_dotdot(cdir->d_name) || !fspathcmp(cdir->d_name, ".git"))
 		return path_none;