[docs] Deprecate the Design Kit docs on Notion

[danilo-leal]

Summary

We're in the process of moving the Design Kits documentation from Notion to the Material UI docs space. This issue is meant to track the Notion deprecation process:

• [x] Move the content to the next branch
• [x] Move the content to the master branch https://mui.com/material-ui/design-resources/material-ui-for-figma/
• [x] Replace Notion links in the Design Kit Figma profile
• [x] Replace Notion links in the Store Design Kit page
• [x] Update /figma/getting-started/ to point to the new docs location (we must have a permalink since we link the docs from the Figma file itself that we can't update) https://github.com/mui/material-ui/pull/42448

Examples

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Motivation

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