Stub GrabCAD Media tests

[ZachOrr]

https://github.com/the-blue-alliance/the-blue-alliance/actions/runs/8370703916/job/22918506267

The following tests are flaky on CI due to loading URLs from an API

src/backend/web/handlers/suggestions/tests/suggest_designs_review_controller_test.py::test_accept_suggestion
src/backend/web/handlers/suggestions/tests/suggest_designs_review_controller_test.py::test_reject_suggestion
src/backend/web/handlers/suggestions/tests/suggest_designs_review_controller_test.py::test_fast_path_accept
src/backend/web/handlers/suggestions/tests/suggest_designs_review_controller_test.py::test_fast_path_reject
src/backend/web/handlers/suggestions/tests/suggest_designs_review_controller_test.py::test_fast_path_already_reviewed

Here's output from one of the tests

____________________________ test_accept_suggestion ____________________________

login_user_with_permission = <Mock spec='User' id='140012527716112'>
ndb_stub = <google.appengine.api.datastore_file_stub.DatastoreFileStub object at 0x7f571d243d10>
web_client = <FlaskClient <Flask 'backend.web.main'>>
taskqueue_stub = <google.appengine.api.taskqueue.taskqueue_stub.TaskQueueServiceStub object at 0x7f571d20cd10>

    def test_accept_suggestion(
        login_user_with_permission,
        ndb_stub,
        web_client: Client,
        taskqueue_stub,
    ) -> None:
>       suggestion_id = createSuggestion(login_user_with_permission)

src/backend/web/handlers/suggestions/tests/suggest_designs_review_controller_test.py:92: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
src/backend/web/handlers/suggestions/tests/suggest_designs_review_controller_test.py:58: in createSuggestion
    status = SuggestionCreator.createTeamMediaSuggestion(
src/backend/common/suggestions/suggestion_creator.py:55: in createTeamMediaSuggestion
    media_dict = MediaParser.partial_media_dict_from_url(media_url)
src/backend/common/suggestions/media_parser.py:107: in partial_media_dict_from_url
    return cls._partial_media_dict_from_grabcad(url)
src/backend/common/suggestions/media_parser.py:267: in _partial_media_dict_from_grabcad
    grabcad_data = json.loads(urlfetch_result.content)
/opt/hostedtoolcache/Python/3.12.2/x64/lib/python3.12/json/__init__.py:346: in loads
    return _default_decoder.decode(s)
/opt/hostedtoolcache/Python/3.12.2/x64/lib/python3.12/json/decoder.py:337: in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <json.decoder.JSONDecoder object at 0x7f575637e5a0>
s = '<?xml version="1.0" encoding="UTF-8"?>\n<Error><Code>AccessDenied</Code><Message>Access Denied</Message><RequestId>YF...79HPX</RequestId><HostId>fcTxJzU1vR3UUzif7pOixSYvtKZ1NxUv0tG4ofBUKhN4Z1OgAAQlc8eXb5V6pqy8z2/jyAHkfnA=</HostId></Error>'
idx = 0

    def raw_decode(self, s, idx=0):
        """Decode a JSON document from ``s`` (a ``str`` beginning with
        a JSON document) and return a 2-tuple of the Python
        representation and the index in ``s`` where the document ended.
    
        This can be used to decode a JSON document from a string that may
        have extraneous data at the end.
    
        """
        try:
            obj, end = self.scan_once(s, idx)
        except StopIteration as err:
>           raise JSONDecodeError("Expecting value", s, err.value) from None
E           json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)

/opt/hostedtoolcache/Python/3.12.2/x64/lib/python3.12/json/decoder.py:355: JSONDecodeError
------------------------------ Captured log call -------------------------------
WARNING  root:media_parser.py:265 Unable to retreive url: https://grabcad.com/community/api/v1/models/2016-148-robowranglers-1

We should stub the response for these GrabCAD urls so we're not hitting an API upstream in our tests