Address review comments on swift-syntax-rs macOS toolchain docs

unified/swift-syntax-rs/BUILD.bazel

@@ -18,14 +18,6 @@ _SWIFT_SUPPORTED_PLATFORMS = select({
 
 # Swift FFI shim: wraps swift-syntax and exposes a small C ABI. The Rust
 # targets below link against its `CcInfo`.
-#
-# On macOS, `rules_swift` auto-registers `xcode_swift_toolchain`, whose
-# analysis fails against Bazel's default `local_config_cc`. To avoid
-# forcing every macOS target in the repo onto the Apple CC toolchain, the
-# Xcode-config flags are applied only along the incoming edge into this
-# `swift_library` via `xcode_transition_swift_library` (see
-# `xcode_transition.bzl`). Downstream Rust targets stay in the default
-# configuration.
 xcode_transition_swift_library(
     name = "swift_syntax_ffi",
     srcs = ["swift/Sources/SwiftSyntaxFFI/SwiftSyntaxFFI.swift"],

unified/swift-syntax-rs/README.md

@@ -148,8 +148,8 @@ Requirements:
   **macOS / `xcode`** (Apple Silicon and Intel). Bazel selects the toolchain
   matching the host. Targets are marked `target_compatible_with` these two
   OSes, so on Windows Bazel skips them cleanly.
-- **macOS only:** the macOS toolchain is a `.pkg` archive that can only be
-  fetched and extracted on a macOS host. On macOS, `rules_swift` also needs
+- **macOS only:** the Swift toolchain comes from the host Xcode installation
+  (`rules_swift` auto-registers `xcode_swift_toolchain`), which also needs
   Xcode's CC toolchain and xcode_config; these are applied to the Swift
   target via an incoming-edge Starlark transition (see
   [`xcode_transition.bzl`](xcode_transition.bzl)), so other targets on macOS