bpo-46659: test.support avoids locale.getdefaultlocale() (GH-31167)

skip_if_buggy_ucrt_strfptime() of test.support now uses
locale.getpreferredencoding(False) instead of
locale.getdefaultlocale() to get the Windows code page.

Lib/test/support/__init__.py

@@ -1421,7 +1421,7 @@ def skip_if_buggy_ucrt_strfptime(test):
     global _buggy_ucrt
     if _buggy_ucrt is None:
         if(sys.platform == 'win32' and
-                locale.getdefaultlocale()[1]  == 'cp65001' and
+                locale.getpreferredencoding(False)  == 'cp65001' and
                 time.localtime().tm_zone == ''):
             _buggy_ucrt = True
         else: