Remove tertiary category from collapse button

What does this MR do and why?

The lack of any border on the collapse button in the environments page made it difficult to separate from the environment name next to it.

The name links to the environment's details page, and there was some confusion that it was separate from the icon.

Changelog: changed

Screenshots or screen recordings

How to set up and validate locally

1. Create some environments

stages:
    - deploy
    - stop
image: alpine:latest

deploy-prod:
    stage: deploy
    script:
        - sleep 10
        - echo "deploying prod"
    environment:
        name: production
        url: postgres://example.com

deploy-staging:
    stage: deploy
    script:
        - echo "deploying staging I hope"
    environment:
        name: staging
        url: https://example.com
    when: manual

deploy-development:
    stage: deploy
    script:
        - echo "deploying development"
    environment:
        name: development
        url: https://example.com
    when: manual

deploy-review:
    stage: deploy
    script:
        - echo "Deploying review/$CI_COMMIT_REF_NAME"
    environment:
        name: review/$CI_COMMIT_REF_NAME
        auto_stop_in: 1 week
    only:
        - branches
    except:
        - main
    when: manual


stop_review_app:
  script: stop-review-app
  stage: stop
  environment:
    name: review/$CI_COMMIT_REF_SLUG
    action: stop
  rules:
    - if: $CI_MERGE_REQUEST_ID
      when: manual

1. Run a pipeline to generate environments
2. View the environments page: Deployments > Environments

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

For #375610 (closed)