tests: rename digraph.gz -> digraph.dot

tests/cli/_dot_test.py

@@ -26,4 +26,4 @@ def test__dot_recurse_dir(capsys):
     _dot()
     out, err = capsys.readouterr()
     assert not err
-    assert out == pathlib.Path("persons").joinpath("digraph.gz").read_text()
+    assert out == pathlib.Path("persons").joinpath("digraph.dot").read_text()