[docs] Fix incorrect `Cases` icon

[PunitSoniME]

• [x] I have followed (at least) the PR section of the contributing guide.

Fixes #33673

Preview: https://deploy-preview-33688--material-ui.netlify.app/material-ui/material-icons/?query=cases

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After - Codesandbox

[mui-bot]

No bundle size changes

Generated by :no_entry_sign: dangerJS against 450594b8fee10f38d3e33f49d9ab8a9ee9785dc5

[PunitSoniME]

Before

After

[michaldudak]

We don't accept PRs to fix individual icons (see https://github.com/mui/material-ui/blob/master/packages/mui-icons-material/README.md#contributing), as we periodically sync the whole set with Google. I'm going to update the whole set, as it hasn't been done in a while. Here's the PR: https://github.com/mui/material-ui/pull/33988.

Unfortunately, the updated set does not include the fixed Cases icon. There is an issue in the Material Icons repo that reports this problem. Please upvote it if you need this icon fixed.