testOooServer: fix test converting invalid file

This test tried tries to convert a broken file, but this broken file was
"not broken enough" and it managed to pass and reply with 200 OK.

Adjust the test to use a "more broken file" that actually cause a 402
return code.

This is because with libreoffice 7.5.2.2 that file was broken enough
to trigger the error, but changing here minimize the changes related to
libreoffice version up.

cloudooo/handler/ooo/tests/testOooServer.py

@@ -141,7 +141,7 @@ class TestConversion(TestCase):
     # Test run_convert method with invalid file
     with open(join('data', 'test.doc'), 'rb') as f:
       scenario_list.append(
-        ('test.doc', f.read()[:300], 200, '',
+        ('test.doc', f.read()[:-300], 402, '',
         ['data', 'meta', 'mime'], '', 'application/vnd.oasis.opendocument.text'
       ))
     return scenario_list