Improve qrencode colors

- Revert commit bb9080c. Changing UTF8 to ANSI256UTF8 does not work
  on e.g. Ubuntu 20.04, and causes an error when showing client
  QR codes.

wireguard-install.sh

@@ -1018,7 +1018,7 @@ start_wg_service() {
 }
 
 show_client_qr_code() {
-	qrencode -t ANSI256UTF8 < "$export_dir$client".conf
+	qrencode -t UTF8 < "$export_dir$client".conf
 	echo -e '\xE2\x86\x91 That is a QR code containing the client configuration.'
 }