Revert "[CMake] Add Locale_Notifications.swift (#726)" (#748)

This reverts commit ab2cd9c.

Author: rintaro

Sources/FoundationEssentials/Locale/CMakeLists.txt

@@ -18,7 +18,6 @@ target_sources(FoundationEssentials PRIVATE
     Locale.swift
     Locale_Autoupdating.swift
     Locale_Cache.swift
-    Locale_Notifications.swift
     Locale_Preferences.swift
     Locale_Protocol.swift
     Locale_Unlocalized.swift)