Remove includes from CI from common

During incident production#3312 (closed) we discovered that we were hardcoding our CI image to latest for the tooling job.

This caused a problem because we are in the middle of testing a change in our CI image that makes helm3 the default.

Given that we have collapsed the number of projects I think we should move our CI includes into gitlab-com and gitlab-helmfiles.

Removing these two sections:

• https://gitlab.com/gitlab-com/gl-infra/k8s-workloads/gitlab-com/-/blob/master/.gitlab-ci.yml#L9-18
• https://gitlab.com/gitlab-com/gl-infra/k8s-workloads/gitlab-helmfiles/-/blob/master/.gitlab-ci.yml#L9-24