pack-objects: remove duplicate --stdin-packs definition

cd846ba (pack-objects: introduce '--stdin-packs=follow', 2025-06-23)
added a new definition of the option --stdin-packs that accepts an
argument.  It kept the old definition, which still shows up in the short
help, but is shadowed by the new one.  Remove it.

Hinted-at-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: rscharfe

builtin/pack-objects.c

@@ -4925,8 +4925,6 @@ int cmd_pack_objects(int argc,
 		OPT_CALLBACK_F(0, "stdin-packs", &stdin_packs, N_("mode"),
 			     N_("read packs from stdin"),
 			     PARSE_OPT_OPTARG, parse_stdin_packs_mode),
-		OPT_BOOL(0, "stdin-packs", &stdin_packs,
-			 N_("read packs from stdin")),
 		OPT_BOOL(0, "stdout", &pack_to_stdout,
 			 N_("output pack to stdout")),
 		OPT_BOOL(0, "include-tag", &include_tag,