Intermittently failing reindex_v2 unit test

Example: https://gitlab.com/arkindex/backend/-/jobs/1183479387

arkindex.documents.tests.commands.test_reindex_v2.TestReindexV2Command.test_run_multiple_elements can fail randomly since the list of indexed documents is not ordered. Maybe use assertCountEqual instead of assertListEqual in all of the reindex_v2 tests?