Standardize FROM statement format in Dockerfiles
Currently, the FROM statements in Dockerfiles are formatted like this:
```docker
ARG BASE_REGISTRY=nexus-docker-secure.levelup-nexus.svc.cluster.local:18082
ARG BASE_IMAGE=gitlab/gitlab/gitlab-ruby
ARG BASE_TAG=15.2.1
ARG RUBY_IMAGE=${BASE_REGISTRY}/${BASE_IMAGE}:${BASE_TAG}
FROM ${RUBY_IMAGE}
```
For DSOP releases, repo1 linter doesn't like the use of the `RUBY_IMAGE` variable so we received a request to modify the release helper script to make all FROM statements look like this for all containers:
```docker
FROM ${BASE_REGISTRY}/${BASE_IMAGE}:${BASE_TAG}
```
Doing this has the added side benefit of simplifying the code in the Release Helper script because the [same script function](https://gitlab.com/gitlab-org/build/dsop-scripts/-/blob/master/release-helper.sh?ref_type=heads) can be used for all containers when releasing GitLab to DSOP
issue