docs: Update the Xcode page.

[folospior]

Removed a misleading note, saying that the library needs to be built from source if using coroutines. Once again, sorry for the bad PR before, this one should be fine now.

Documentation change checklist

• [x] My documentation changes follow the docs style guide and any code examples follow the coding style guide.
• [x] I tested that my change works before raising the PR (via running doxygen, and testing examples).
• [x] I have not moved any existing pages or changed any existing URLs without strong justification as to why.
• [x] I have not generated content using AI or a desktop utility such as grammarly.

[github-actions[bot]]

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