gitlab: Move to the latest docker image
This enables support for testing U-Boot vboot.
BRANCH=none
TEST=passes on gitlab:
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
-image: jbettis/ubuntu-29sep21
+image: sjg20/ubuntu-25feb22c
# You can update that image using this repo:
# https://gitlab.com/zephyr-ec/gitlab-ci-runner/-/tree/main
