merge: mark usage error strings for translation

The nearby error messages are already marked for
translation, but these new ones aren't.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

builtin/merge.c

@@ -1164,7 +1164,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		const char *nargv[] = {"reset", "--merge", NULL};
 
 		if (orig_argc != 2)
-			usage_msg_opt("--abort expects no arguments",
+			usage_msg_opt(_("--abort expects no arguments"),
 			      builtin_merge_usage, builtin_merge_options);
 
 		if (!file_exists(git_path_merge_head()))
@@ -1180,7 +1180,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		const char *nargv[] = {"commit", NULL};
 
 		if (orig_argc != 2)
-			usage_msg_opt("--continue expects no arguments",
+			usage_msg_opt(_("--continue expects no arguments"),
 			      builtin_merge_usage, builtin_merge_options);
 
 		if (!file_exists(git_path_merge_head()))