[CI] Align environment names in stable, production jobs

What does this MR do?

Fix environment names in stable, production jobs

Aligns the environment names for the stable and production jobs.

Without this fix, we can see that environment names for
QA jobs show `/master` in the environment name while the
production_specs_* and stable_* jobs don't have that suffix.

Example:
https://gitlab.com/gitlab-org/charts/gitlab/-/pipelines/844963103

Related issues

Closes #4637 (closed)

Testing notes

Confirming that each environment name aligns:

$ yq 'with_entries(select(.value | has("environment"))) | to_entries | .[] | .value.environment.name' .gitlab-ci.yml | grep 'production' | sort | uniq
eks_production
gke122_production
gke125_production
gke_production

Compare this to the result from master ❌

$ yq 'with_entries(select(.value | has("environment"))) | to_entries | .[] | .value.environment.name' .gitlab-ci.yml | grep 'production' | sort | uniq
eks_production
eks_production/$REVIEW_REF_PREFIX$CI_COMMIT_REF_SLUG
gke122_production
gke122_production/$REVIEW_REF_PREFIX$CI_COMMIT_REF_SLUG
gke125_production
gke125_production/$REVIEW_REF_PREFIX$CI_COMMIT_REF_SLUG
gke_production
gke_production/$REVIEW_REF_PREFIX$CI_COMMIT_REF_SLUG

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion.

Required

• Merge Request Title and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com
• When ready for review, MR is labeled "~workflow::ready for review" per the Distribution MR workflow

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Tests added
• Integration tests added to GitLab QA
• Equivalent MR/issue for omnibus-gitlab opened
• Validate potential values for new configuration settings. Formats such as integer 10, duration 10s, URI scheme://user:passwd@host:port may require quotation or other special handling when rendered in a template and written to a configuration file.