Update Docker images used by CI templates

docker stable tags are no longer supported or being updated

Switch https://gitlab.developers.cam.ac.uk/uis/devops/continuous-delivery/ci-templates/-/blob/master/auto-devops/tox-tests.yml#L61 and https://gitlab.developers.cam.ac.uk/uis/devops/continuous-delivery/ci-templates/-/blob/master/auto-devops/tox-tests.yml#L64 to docker:git and docker:dind.

UPDATE (@dkh21): Expanded scope of this issue to cover all CI templates using the stable tags.