Upgrade global styles (#12167)
* website: upgrade global-styles packages
* website: remove deprecated --site-max-width on community page
* website: replace code-block showWindowBar with showChrome
* website: replace old g-container with g-grid-container
* website: backfill missing type styles
* website: revert change to heading semantics
* website: fix mismatched border colour
* website: fix spacing issue
* website: revert accidental replacement
* website: clarify debt intention with comment
* website: fix missing search styles, remove cruft
* website: hide alert-banner on mobile
* website: bump to latest patched dependencies
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