Improve the change made in the previous commit.

doshell() never returns, so there is no need to see whether we are the
parent process.

usr.bin/script/script.c

@@ -158,8 +158,7 @@ main(int argc, char *argv[])
 	}
 	if (child == 0)
 		doshell(argv);
-	else
-		close(slave);
+	close(slave);
 
 	if (flushtime > 0)
 		tvp = &tv;