remove `directory_entry::clear_cache` (#2854)

stl/inc/filesystem

@@ -2175,12 +2175,6 @@ namespace filesystem {
             }
         }
 
-#if _HAS_CXX20
-        void clear_cache() noexcept {
-            _Cached_data._Available = __std_fs_stats_flags::_None;
-        }
-#endif // _HAS_CXX20
-
     private:
         _NODISCARD bool _Has_cached_attribute(const __std_fs_file_attr _Attrs) const noexcept {
             return _Bitmask_includes(_Cached_data._Attributes, _Attrs);

stl/inc/yvals_core.h

@@ -273,7 +273,6 @@
 // P2415R2 What Is A view?
 // P2418R2 Add Support For std::generator-like Types To std::format
 // P2432R1 Fix istream_view
-// P????R? directory_entry::clear_cache()
 
 // _HAS_CXX20 indirectly controls:
 // P0619R4 Removing C++17-Deprecated Features

tests/std/tests/P0218R1_filesystem/test.cpp

@@ -1200,18 +1200,6 @@ void test_directory_entry() {
     EXPECT(good(ec));
     EXPECT(cachingEntry.is_regular_file(ec));
     EXPECT(good(ec));
-#if _HAS_CXX20
-    // break caching again, and assert that things aren't cached
-    cachingEntry.clear_cache();
-    EXPECT(cachingEntry.file_size(ec) == static_cast<uintmax_t>(-1));
-    EXPECT(bad(ec));
-    EXPECT(cachingEntry.last_write_time(ec) == file_time_type::min());
-    EXPECT(bad(ec));
-    EXPECT(cachingEntry.hard_link_count(ec) == static_cast<uintmax_t>(-1));
-    EXPECT(bad(ec));
-    EXPECT(!cachingEntry.is_regular_file(ec));
-    EXPECT(bad(ec));
-#endif // _HAS_CXX20
 
     // assert that mutating the path doesn't fail even though the target doesn't exist
     for (auto&& nonexistent : nonexistentPaths) {