TUN-7590: Remove usages of ioutil

tunneldns/https_upstream.go

@@ -5,7 +5,7 @@ import (
 	"context"
 	"crypto/tls"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"net"
 	"net/http"
 	"net/url"
@@ -105,7 +105,7 @@ func exchangeWireformat(msg []byte, endpoint *url.URL, client *http.Client) ([]b
 	}
 
 	// Read wireformat response from the body
-	buf, err := ioutil.ReadAll(resp.Body)
+	buf, err := io.ReadAll(resp.Body)
 	if err != nil {
 		return nil, errors.Wrap(err, "failed to read the response body")
 	}