all: replace uses of ioutil with io and os (#24869)

p2p/discover/v5wire/encoding_test.go

@@ -23,7 +23,6 @@ import (
 	"errors"
 	"flag"
 	"fmt"
-	"io/ioutil"
 	"net"
 	"os"
 	"path/filepath"
@@ -580,7 +579,7 @@ func (n *handshakeTestNode) id() enode.ID {
 // hexFile reads the given file and decodes the hex data contained in it.
 // Whitespace and any lines beginning with the # character are ignored.
 func hexFile(file string) []byte {
-	fileContent, err := ioutil.ReadFile(file)
+	fileContent, err := os.ReadFile(file)
 	if err != nil {
 		panic(err)
 	}