* docs: fix macOS tier 1 targets and platform compatibility table
- Add aarch64-apple-darwin to the tier 1 macOS target list.
- Use feat_os_unix for macOS in uudoc.rs, since feat_os_macos does not
exist and caused the compatibility table to show almost no macOS
support.
* uudoc: remove unnecessary comment about macOS feature
* uudoc: drop macos feature entry and use unix for macOS