doc txt & -h consistency: add "-z" to cat-file "-h"

Fix a bug in db9d67f (builtin/cat-file.c: support NUL-delimited
input with `-z`, 2022-07-22), before that change the SYNOPSIS and "-h"
output were the same, but not afterwards.

That change followed a similar earlier divergence in
473fa2d (Documentation: add --batch-command to cat-file synopsis,
2022-04-07). Subsequent commits will fix this sort of thing more
systematically, but let's fix this one as a one-off.

Signed-off-by: Ævar Arnfjörð Bjarmason <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: avar

builtin/cat-file.c

@@ -893,7 +893,7 @@ int cmd_cat_file(int argc, const char **argv, const char *prefix)
 		N_("git cat-file (-t | -s) [--allow-unknown-type] <object>"),
 		N_("git cat-file (--batch | --batch-check | --batch-command) [--batch-all-objects]\n"
 		   "             [--buffer] [--follow-symlinks] [--unordered]\n"
-		   "             [--textconv | --filters]"),
+		   "             [--textconv | --filters] [-z]"),
 		N_("git cat-file (--textconv | --filters)\n"
 		   "             [<rev>:<path|tree-ish> | --path=<path|tree-ish> <rev>]"),
 		NULL