Return registry strings of each_value and each_key as UTF-8

Since ruby-3.0 usually all strings from the Windows-API are returned as UTF-8 strings.
Win32::Registry partly returned OEM encoding.
This was a leftover from 2.x times.
This commit changes it to UTF-8.

Fixes: oneclick/rubyinstaller2#348

lib/win32/registry.rb

@@ -69,11 +69,7 @@ module Win32
   WCHAR_NUL = "\0".encode(WCHAR).freeze
   WCHAR_CR = "\r".encode(WCHAR).freeze
   WCHAR_SIZE = WCHAR_NUL.bytesize
-  begin
-    LOCALE = Encoding.find(Encoding.locale_charmap)
-  rescue ArgumentError
-    LOCALE = Encoding::UTF_8
-  end
+  LOCALE = Encoding::UTF_8
 
   class Registry