Mark test_clone_command_injection xfail on Windows

This other GitCommandError on Windows is not related to
IndexFile.from_tree whose 8 related failing tests were marked xfail
in the preceding commit.

Also, test_clone_command_injection should not be confused with
test_clone_from_command_injection, which passes on all platforms.

The problem here appears to be that, on Windows, the path of the
directory GitPython is intended to clone to -- when the possible
security vulnerability this test checks for is absent -- is not
valid. This suggests the bug may only be in the test and that the
code under test may be working on Windows. But the test does not
establish that, for which it would need to test with a payload
clearly capable of creating the file unexpected_path refers to when
run on its own. (The "\" characters in the path seem to be treated
as escape characters rather than literally. Also, "touch" is not a
native Windows command, and the "touch" command in Git for Windows
maps disallowed occurrences of ":" in filenames to a separate code
point in the Private Use Area of the Basic Multilingual Plane.)

This doesn't currently seem to be reported as a bug, but some
general context about the implementation can be examined in gitpython-developers#1518
where it was introduced, and gitpython-developers#1531 where it was modified.

test/test_repo.py

@@ -1365,6 +1365,11 @@ def test_do_not_strip_newline_in_stdout(self, rw_dir):
         r.git.commit(message="init")
         self.assertEqual(r.git.show("HEAD:hello.txt", strip_newline_in_stdout=False), "hello\n")
 
+    @pytest.mark.xfail(
+        os.name == "nt",
+        reason=R"fatal: could not create leading directories of '--upload-pack=touch C:\Users\ek\AppData\Local\Temp\tmpnantqizc\pwn': Invalid argument",  # noqa: E501
+        raises=GitCommandError,
+    )
     @with_rw_repo("HEAD")
     def test_clone_command_injection(self, rw_repo):
         with tempfile.TemporaryDirectory() as tdir: