CSS changes for checkbox

[MylesJarvis]

Trello card

https://trello.com/c/nDfEHJnU

Context

• We introduced some CSS in our Gov Frontend 5.2 upgrade due to a bug we identified in the candidate search function.
• However, this had knock on impacts on other areas of the system, mainly on the school side.
• This fix removes the code we introduced as part of that Frontend upgrade, but also removes some stray CSS which seems to be causing the issue with checkboxes.

Changes proposed in this pull request

Guidance to review

[github-actions[bot]]

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