Fixed aria-hidden value

What does this MR do?

Fixes aria-hidden values across the application as they are currently invalid with a boolean value as they then produce an aria-hidden instead of the correct aria-hidden="true". This simply converts all instances to a string value.

See - https://validator.w3.org/nu/?doc=https%3A%2F%2Fgitlab.com%2Fexplore

Fixed on https://gitlab-review-tz-fix-ari-urk79u.gitlab-review.app/explore

Does this MR meet the acceptance criteria?

Conformity

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• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
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Security

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• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
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