Don't mock the lchmod functions, and explain why

This undoes the mocking of lchmod functions from e309b35, and
instead notes why they may be better left alone in the tests.

This also rewords the existing comment to better explain the reason
for the mocking that is being done.

Author: EliahKagan

test/test_util.py

@@ -140,15 +140,11 @@ def _patch_for_wrapping_test(self, mocker, hide_windows_known_errors):
         # git.index.util "replaces" git.util and is what "import git.util" gives us.
         mocker.patch.object(sys.modules["git.util"], "HIDE_WINDOWS_KNOWN_ERRORS", hide_windows_known_errors)
 
-        # Disable some chmod functions so the callback can't fix a PermissionError.
+        # Mock out common chmod functions to simulate PermissionError the callback can't
+        # fix. (We leave the corresponding lchmod functions alone. If they're used, it's
+        # more important we detect any failures from inadequate compatibility checks.)
         mocker.patch.object(os, "chmod")
-        if hasattr(os, "lchmod"):
-            # Exists on some operating systems. Mocking out os.chmod doesn't affect it.
-            mocker.patch.object(os, "lchmod")
         mocker.patch.object(pathlib.Path, "chmod")
-        if hasattr(pathlib.Path, "lchmod"):
-            # Exists on some Python versions. Don't rely on it calling a public chmod.
-            mocker.patch.object(pathlib.Path, "lchmod")
 
     @pytest.mark.skipif(
         os.name != "nt",