Apply external repo transforms to all migrated files

This ensures that markdown files also have //third_party/* labels changed to external-friendly @foo// labels.

PiperOrigin-RevId: 694229457
Change-Id: I7f3bd56f0a196112a82159d6f47f8285049fc324

docs/toolchain_api.md

@@ -700,11 +700,11 @@ When building a [`cc_toolchain`](#cc_toolchain) configuration, it's important to
 statements will be evaluated:
 
 * Most attributes and dependencies of a [`cc_toolchain`](#cc_toolchain) are evaluated under the target platform.
-  This means that a `//third_party/bazel_platforms/os:linux` constraint will be satisfied when
+  This means that a `@platforms//os:linux` constraint will be satisfied when
   the final compiled binaries are intended to be ran from a Linux machine. This means that
   a different operating system (e.g. Windows) may be cross-compiling to linux.
 * The [`cc_tool_map`](#cc_tool_map) rule performs a transition to the exec platform when evaluating tools. This
-  means that a if a `//third_party/bazel_platforms/os:linux` constraint is satisfied in a
+  means that a if a `@platforms//os:linux` constraint is satisfied in a
   `select` statement on a [`cc_tool`](#cc_tool), that means the machine that will run the tool is a Linux
   machine. This means that a Linux machine may be cross-compiling to a different OS
   like Windows.