build: docusaurus 3.5 upgrade

[erickzhao]

Updates to Docusaurus 3.5.

• Reverts 1f8a694331c4d7be7c86528a1ebb5b6af6648271 since the feature was upstreamed. Removed patch-package since we don't need patches anymore.
• Added mdast-util-mdx to the dependency tree so that we can pass it in as an extension to toMarkdown(). We do some hacky Markdown -> MDAST -> Markdown conversion in the API structure preview transformer that now has an MDX node by default as of https://github.com/facebook/docusaurus/pull/10335 so this is needed to render those previews now.
• Changed an internal import that was updated in the latest version.

[dsanders11]

This got merged as I was writing this up. 😅

Looks like there's a few visual changes to the blog as a result of this PR. Not to bikeshed too much, but I kind prefer some parts of the blog sidebar as they currently are, like the border below the title. I wonder if we can retain any of those styles without needing to swizzle the whole component?

The blog author name not being centered vertically looks to be intentional but IMO is awkward looking. Looks like if we used the new authors pages features and put author's GitHub as a social it might render better.

Before:

After: