test: Update tagged openassessment test

[yusuf-musleh]

Description

This updates the tests related to tagged openassessment blocks to avoid hardcoding the serialized olx that causes issues when attributes are added/removed down the road. See #34145 (comment)

Testing instructions

Make sure the tests pass.

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[yusuf-musleh]

@feanil Seems like one of the tests failed unexpectedly, just says that the job failed. Can you please rerun the remaining tests?

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[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX staging environment in preparation for a release to production.

[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX production environment.

[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX production environment.