Fix stage name escaping in pipeline views

What does this MR do and why?

Stage names in the pipeline overview and in the pipeline editor visualise view were rendered in an escaped and capitalized format.

This happened because of a manual capitalization and escaping, which is removed in this MR in favour of Vue.js native escaping.

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Create .gitlab-ci.yaml file with "escapable" characters in stage names, e.g.

stages:
  - Test & LINT

test-lint:
  stage: Test & LINT
  script:
    - echo "TEST AND LINT"

2. Check the stage name in pipeline overview for the running pipeline, the name should be exactly as defined in the CI file
3. Check the stage name in pipeline editor visualize view, the name should be exactly as defined in the CI file

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.

Fixes #24922 (closed)