fix sample

beautiful-racket-demo/basic-demo-3/sample-gosub.rkt

@@ -1,10 +1,10 @@
 #lang basic-demo-3
 10 gosub 41
-20 print "world"
+20 print "second"
 30 gosub 100
-31 print "hi"
+31 print "fourth"
 35 end
 40 return
-41 print "hello" : return
+41 print "first" : return
 100 print "third"
 110 goto 40