usage: mark the -J/--guidestripe option plus argument as translatable

This fixes https://savannah.gnu.org/bugs/?56930.

Bug existed since the vertical guiding bar was introduced,
in version 4.0, commit 66c6eb51.

src/nano.c

@@ -739,7 +739,7 @@ void usage(void)
 	print_opt("-I", "--ignorercfiles", N_("Don't look at nanorc files"));
 #endif
 #ifndef NANO_TINY
-	print_opt("-J <number>", "--guidestripe=<number>",
+	print_opt(_("-J <number>"), _("--guidestripe=<number>"),
 					N_("Show a guiding bar at this column"));
 #endif
 	print_opt("-K", "--rawsequences",