Does not build on Xcode 16

[bolot]

Currently, Enchanted fails to build with Xcode 16 due to the code in https://github.com/AugustDev/swift-markdown-ui.

The same issue has been addressed in the upstream https://github.com/gonzalezreal/swift-markdown-ui in this PR:

• Fix circular reference error gonzalezreal/swift-markdown-ui#328

It might make sense to reset the forked swift-markdown-ui's main branch to match the upstream repo, since the previously-cherry-picked PR has been merged:

• Add title bar for code blocks in the Demo app CodeSyntaxHighlightView gonzalezreal/swift-markdown-ui#249