stow: remove misleading comment about current dir

The current directory is changed by within_target_do() which is called
by `plan_stow()`, `plan_unstow()`, and `process_tasks()`.  It is not
changed when constructing a new `Stow` object, so remove this outdated
and misleading comment.

Fixes #102.

bin/stow.in

@@ -474,7 +474,6 @@ sub main {
     my ($options, $pkgs_to_unstow, $pkgs_to_stow) = process_options();
 
     my $stow = new Stow(%$options);
-    # current dir is now the target directory
 
     $stow->plan_unstow(@$pkgs_to_unstow);
     $stow->plan_stow  (@$pkgs_to_stow);