tests: fix test_bytes

%p has different casing with mingw-w64, but it's implementation defined.
Change the test to the mingw-w64 variant.

Author: lazka

Lib/test/test_bytes.py

@@ -1105,7 +1105,7 @@ def test_from_format(self):
 
         if os.name == 'nt':
             # Windows (MSCRT)
-            ptr_format = '0x%0{}X'.format(2 * sizeof_ptr)
+            ptr_format = '0x%0{}x'.format(2 * sizeof_ptr)
             def ptr_formatter(ptr):
                 return (ptr_format % ptr)
         else: