feat: add frontend-app-admin-portal to whitelisted origins

[hamzawaleed01]

Description

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Design decisions and their rationales should be documented in the repo (docstring / ADR), per
OEP-19, and can be
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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.