Pin dind image to 23.0.6

What does this MR do?

This MR is a fix for the issue described here, which causes the custom-ca job to fail with the following error:

$ docker run -d --name ssl-test --net ssl-test $SSL_SERVER
79ded442ebff71cbf44f905e9561bc395e0d8bb4940f75c823a7521e5fd9d553
docker: Error response from daemon: cgroups: cgroup mountpoint does not exist: unknown.

Pinning to a more recent version of docker:dind should fix the issue.

What are the relevant issue numbers?

Investigate failing custom-ca jobs in secure-te... (gitlab-org/gitlab#415134 - closed)