[libc++] Remove <experimental/filesystem> header
`<filesystem>` header has been around for a while now, so we can safely remove
`<experimental/filesystem>` header. `_LIBCPP_DEPRECATED_EXPERIMENTAL_FILESYSTEM`
suggests we were going to remove `<experimental/filesystem>` in llvm 11 release,
but we never did. So, remove the experimental header now, its associated tests,
and the `_LIBCPP_DEPRECATED_EXPERIMENTAL_FILESYSTEM` macro.
Differential Revision: https://reviews.llvm.org/D119603
NOKEYCHECK=True
GitOrigin-RevId: 861386dbd6ff0d91636b7c674c2abb2eccd9d3f2
diff --git a/docs/ReleaseNotes.rst b/docs/ReleaseNotes.rst
index 0bf24b9..58b4506 100644
--- a/docs/ReleaseNotes.rst
+++ b/docs/ReleaseNotes.rst
@@ -46,6 +46,9 @@
they were not supposed to set ``_LIBCPP_ABI_UNSTABLE`` manually, however we
still feel that it is worth mentioning in the release notes in case some users
had been doing it.
+- The header ``<experimental/filesystem>`` has been removed. Instead, use
+ ``<filesystem>`` header. The associated macro
+ ``_LIBCPP_DEPRECATED_EXPERIMENTAL_FILESYSTEM`` has also been removed.
ABI Changes
-----------