[BUG] Update Labelbox integration to support new API for assigning users to projects

[ehofesmann]

When attempting to run the code in this section: https://docs.voxel51.com/integrations/labelbox.html#configuring-labelbox-projects

I got this error:

File ~/work/fiftyone/fiftyone/fiftyone/utils/annotations.py:250, in annotate(samples, anno_key, label_schema, label_field, label_type, classes, attributes, mask_targets, allow_additions, allow_deletions, allow_label_edits, allow_index_edits, allow_spatial_edits, media_field, backend, launch_editor, **kwargs)
    245 # Don't allow overwriting an existing run with same `anno_key`, since we
    246 # need the existing run in order to perform workflows like automatically
    247 # cleaning up the backend's tasks
    248 anno_backend.register_run(samples, anno_key, overwrite=False)
--> 250 results = anno_backend.upload_annotations(
    251     samples, anno_key, launch_editor=launch_editor
    252 )
    254 anno_backend.save_run_results(samples, anno_key, results)
    256 return results

File ~/work/fiftyone/fiftyone/fiftyone/utils/labelbox.py:195, in LabelboxBackend.upload_annotations(self, samples, anno_key, launch_editor)
    192 api = self.connect_to_api()
    194 logger.info("Uploading media to Labelbox...")
--> 195 results = api.upload_samples(samples, anno_key, self)
    196 logger.info("Upload complete")
    198 if launch_editor:

File ~/work/fiftyone/fiftyone/fiftyone/utils/labelbox.py:653, in LabelboxAnnotationAPI.upload_samples(self, samples, anno_key, backend)
    651 if members:
    652     for email, role in members:
--> 653         self.add_member(project, email, role)
    655 project_id = project.uid
    656 id_map = {}

File ~/work/fiftyone/fiftyone/fiftyone/utils/labelbox.py:415, in LabelboxAnnotationAPI.add_member(self, project, email, role)
    406     logger.warning(
    407         "Your organization has reached its limit of %d members. "
    408         "Cannot invite new member %s to project '%s'",
   (...)
    411         project.name,
    412     )
    413     return
--> 415 project_role = lbs.organization.ProjectRole(
    416     project=project, role=role_id
    417 )
    419 organization.invite_user(
    420     email, self.roles["NONE"], project_roles=[project_role]
    421 )

AttributeError: module 'labelbox.schema.organization' has no attribute 'ProjectRole'