Investigate and resolve optimizely-sdk constraint

[UsamaSadiq]

Description

• optimizely-sdk==5.0.0 started breaking tests [ common/djangoapp/tests/test_views.py::SAMLMetadataTest::test_secure_key_configuration ]
• The package was pinned in the PR to resolve the test failures.
• Investigate the underlying reason, fix and remove the constraint.

[robrap]

@jristau1984: I want to bring this ticket to your attention, because it brings up interesting issues:

1. If we don't maintain edx-platform, Axim may wish to pull out 2U specific dependencies. See https://github.com/openedx/edx-platform/blob/master/requirements/edx/bundled.in
2. As we potentially move more dependencies to be private dependencies, we don't have a great upgrade story for these private dependencies. I think this may be ticketed somewhere, but I'm not sure. And as can be seen by this ticket, how and where will we run tests with our dependencies?