Fix redundancy in error message

Discussion: https://www.postgresql.org/message-id/flat/E1vEsbx-004QDO-0o%40gemulon.postgresql.org

src/bin/pg_basebackup/pg_createsubscriber.c

@@ -668,7 +668,7 @@ modify_subscriber_sysid(const struct CreateSubscriberOptions *opt)
 		int			rc = system(cmd_str);
 
 		if (rc == 0)
-			pg_log_info("subscriber successfully reset WAL on the subscriber");
+			pg_log_info("successfully reset WAL on the subscriber");
 		else
 			pg_fatal("could not reset WAL on subscriber: %s", wait_result_to_str(rc));
 	}