diff: -G description: Correct copy/paste error

Current description for -G is incorrect, seems like it was copied from
the description for -S.

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

Author: ilya-bobyr

diff.c

@@ -5866,7 +5866,7 @@ struct option *add_diff_options(const struct option *opts,
 			       N_("look for differences that change the number of occurrences of the specified string"),
 			       0, diff_opt_pickaxe_string),
 		OPT_CALLBACK_F('G', NULL, options, N_("<regex>"),
-			       N_("look for differences that change the number of occurrences of the specified regex"),
+			       N_("look for differences where a patch contains the specified regex"),
 			       0, diff_opt_pickaxe_regex),
 		OPT_BIT_F(0, "pickaxe-all", &options->pickaxe_opts,
 			  N_("show all changes in the changeset with -S or -G"),