gh-105751: Remove platform usage in test_ctypes (#105819)

The MACHINE variable is no longer used in test_structures.

Author: vstinner

Lib/test/test_ctypes/test_structures.py

@@ -1,5 +1,4 @@
 import _ctypes_test
-import platform
 import struct
 import sys
 import unittest
@@ -12,12 +11,6 @@
 from test import support
 
 
-# The following definition is meant to be used from time to time to assist
-# temporarily disabling tests on specific architectures while investigations
-# are in progress, to keep buildbots happy.
-MACHINE = platform.machine()
-
-
 class SubclassesTest(unittest.TestCase):
     def test_subclass(self):
         class X(Structure):