[libcxx] Remove nonstandard _FilesystemClock::{to,from}_time_t
These are not standard methods, neither libstdc++ nor MSVC STL provide
them.
In practice, one of them was untested and the other one was only used in
one single test.
Differential Revision: https://reviews.llvm.org/D113027
NOKEYCHECK=True
GitOrigin-RevId: 341cc1b4113223352c99199f7c26ea7329d00fb7
diff --git a/docs/ReleaseNotes.rst b/docs/ReleaseNotes.rst
index d2713a9..5f81b3e 100644
--- a/docs/ReleaseNotes.rst
+++ b/docs/ReleaseNotes.rst
@@ -78,6 +78,10 @@
exceeds the maximum supported size, as required by the C++ standard.
Previously the type ``std::length_error`` was used.
+- Removed the nonstandard methods ``std::chrono::file_clock::to_time_t`` and
+ ``std::chrono::file_clock::from_time_t``; neither libstdc++ nor MSVC STL
+ had such methods.
+
ABI Changes
-----------