Replace deprecated ioutil functions with others (#374)

* Remove use of deprecated ioutil functions from examples

* Remove usage of ioutil from gobyexample's own scripts

+ regenerate output

examples/spawning-processes/spawning-processes.go

@@ -9,7 +9,7 @@ package main
 
 import (
 	"fmt"
-	"io/ioutil"
+	"io"
 	"os/exec"
 )
 
@@ -46,7 +46,7 @@ func main() {
 	grepCmd.Start()
 	grepIn.Write([]byte("hello grep\ngoodbye grep"))
 	grepIn.Close()
-	grepBytes, _ := ioutil.ReadAll(grepOut)
+	grepBytes, _ := io.ReadAll(grepOut)
 	grepCmd.Wait()
 
 	// We omitted error checks in the above example, but

examples/spawning-processes/spawning-processes.hash

@@ -1,2 +1,2 @@
-6a62e3109c483c2b52a99905dc1ba5c8cb2a281b
-m2CpSlHPEVq
+b6e1e4b70a494be9f344a9f31aff520116d0ac24
+YJs_YtJY0sS