Remove link to parent pipeline from the badge

What does this MR do and why?

This MR removes a link to the parent pipeline from the badge on the child pipeline header. The link is not rendering correctly inside the badge in dark mode. Also, having a link as part of the badge is not recommended by the Pajamas guidelines.

The parent pipeline link is already available below on the same page, so we are not losing any navigation.

References

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Create a parent pipeline config, example:

stages:          
  - build
  - test
  - deploy

build-job:       
  stage: build
  script:
    - echo "Compiling the code..."
    - echo "Compile complete."

trigger_job:
  trigger:
    include:
      - local: child-pipeline.yml
  environment: production

2. Create the child pipeline config, example:

downstream-job:       
  stage: test
  script:
    - echo "Compiling the code..."
    - echo "Compile complete."

3. Navigate to the pipeline page and verify the child pipeline has a correct badge in the header.

MR acceptance checklist

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Related to #555375 (closed)