Revert "bpo-33671: Add support.MS_WINDOWS and support.MACOS (GH-7800)" (GH-7919)

This reverts commit 8fbbdf0c3107c3052659e166f73990b466eacbb0.
diff --git a/Lib/test/test_shutil.py b/Lib/test/test_shutil.py
index b3b3e66..7e0a329 100644
--- a/Lib/test/test_shutil.py
+++ b/Lib/test/test_shutil.py
@@ -33,6 +33,7 @@
 from test.support import TESTFN, FakePath
 
 TESTFN2 = TESTFN + "2"
+MACOS = sys.platform.startswith("darwin")
 try:
     import grp
     import pwd
@@ -1807,7 +1808,7 @@
 
         self.assertRaises(OSError, shutil.copyfile, 'srcfile', 'destfile')
 
-    @unittest.skipIf(support.MACOS, "skipped on macOS")
+    @unittest.skipIf(MACOS, "skipped on macOS")
     def test_w_dest_open_fails(self):
 
         srcfile = self.Faux()
@@ -1827,7 +1828,7 @@
         self.assertEqual(srcfile._exited_with[1].args,
                          ('Cannot open "destfile"',))
 
-    @unittest.skipIf(support.MACOS, "skipped on macOS")
+    @unittest.skipIf(MACOS, "skipped on macOS")
     def test_w_dest_close_fails(self):
 
         srcfile = self.Faux()
@@ -1850,7 +1851,7 @@
         self.assertEqual(srcfile._exited_with[1].args,
                          ('Cannot close',))
 
-    @unittest.skipIf(support.MACOS, "skipped on macOS")
+    @unittest.skipIf(MACOS, "skipped on macOS")
     def test_w_source_close_fails(self):
 
         srcfile = self.Faux(True)
@@ -2184,7 +2185,7 @@
             shutil._HAS_SENDFILE = True
 
 
-@unittest.skipIf(not support.MACOS, 'macOS only')
+@unittest.skipIf(not MACOS, 'macOS only')
 class TestZeroCopyMACOS(_ZeroCopyFileTest, unittest.TestCase):
     PATCHPOINT = "posix._fcopyfile"