tests: fix compatibility with Python 3.12's unittest.mock

`called_with` was likely not the right call to make, since this
would return a mock instance. Instead, use `assert_called_with`.

See: python/cpython#100690

Author: NicolasT

tests/test_checksum.py

@@ -49,7 +49,7 @@ def test__posix_fadvise_sequential(
         # Make mypy happy
         assert hasattr(os, "POSIX_FADV_SEQUENTIAL")
 
-        assert mocked.called_with(
+        mocked.assert_called_with(
             fd.fileno(),
             0,
             os.fstat(fd.fileno()).st_size,