fix: aria-hidden was applied to the wrong div inside MdTooltip

[aurorascharff]

Describe your changes

Previously aria-hidden had been applied to the children the tooltip is wrapping content rather than the tooltip content itself. This caused errors in the console when the focus was trying target to the content.

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• [x] I have performed a self-review and test of my code
• [x] I have added label to the PR (major, minor or patch)
• [ ] If new component: Is story for component created in stories-folder?
• [ ] If new component: Is tsx-file import added to packages/react/index.tsx?
• [ ] If new component: Is css-file added to packages/css/index.css?

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