Replace toggle button in MR collapsible extension with GlButton

What does this MR do and why?

Replaces toggle button in the MR collapsible extension with GlButton and uses the correct chevron size to be consistent with the other toggle buttons on the MR page.

Screenshots or screen recordings

Before	After
Screen_Recording_2023-01-04_at_4.54.36_PM	Screen_Recording_2023-01-04_at_4.25.15_PM

How to set up and validate locally

Open an MR with artifacts, e.g., by setting up a project with Accessibility Scanning.

Alternatively, add the following to the .gitlab-ci.yml:

test-multi-1:
  script:
    - echo time > time.txt
    - mkdir job-test
    - echo time > job-test/time2.html
  artifacts:
    paths: [time.txt, job-test/time2.html]
    expose_as: "more_artifacts-available_here"

test-multi-2:
  script:
    - mkdir job-test
    - echo time > job-test/time1.html
    - echo time > job-test/time2.html
  artifacts:
    paths: [job-test/]
    expose_as: "this is a - directory"

test-single-1:
  script:
    - echo time > time.txt
  artifacts:
    paths: [time.txt]
    expose_as: "time is here"

test-single-2:
  script:
    - mkdir job-test
    - echo time > job-test/time2.html
  artifacts:
    paths: [job-test/time2.html]
    expose_as: "time2 is here"

test-single-3:
  script:
    - echo time > time.txt
  artifacts:
    paths: [time.txt]
    expose_as: "time is here"

#test-error:
#  script:
#    - echo time > time.txt
#  artifacts:
#    paths: ['*.txt']
#    expose_as: "should not show"

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.

Related to #365243 (closed)