checkout-index: remove obsolete comment

The first paragraph about flag order is no longer true and is
mentioned in git-checkout-index.txt. The rest is also mentioned in
git-checkout-index.txt.

Remove it and keep uptodate document in one place.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/checkout-index.c

@@ -3,38 +3,6 @@
  *
  * Copyright (C) 2005 Linus Torvalds
  *
- * Careful: order of argument flags does matter. For example,
- *
- *	git checkout-index -a -f file.c
- *
- * Will first check out all files listed in the cache (but not
- * overwrite any old ones), and then force-checkout "file.c" a
- * second time (ie that one _will_ overwrite any old contents
- * with the same filename).
- *
- * Also, just doing "git checkout-index" does nothing. You probably
- * meant "git checkout-index -a". And if you want to force it, you
- * want "git checkout-index -f -a".
- *
- * Intuitiveness is not the goal here. Repeatability is. The
- * reason for the "no arguments means no work" thing is that
- * from scripts you are supposed to be able to do things like
- *
- *	find . -name '*.h' -print0 | xargs -0 git checkout-index -f --
- *
- * or:
- *
- *	find . -name '*.h' -print0 | git checkout-index -f -z --stdin
- *
- * which will force all existing *.h files to be replaced with
- * their cached copies. If an empty command line implied "all",
- * then this would force-refresh everything in the cache, which
- * was not the point.
- *
- * Oh, and the "--" is just a good idea when you know the rest
- * will be filenames. Just so that you wouldn't have a filename
- * of "-a" causing problems (not possible in the above example,
- * but get used to it in scripting!).
  */
 #include "builtin.h"
 #include "cache.h"