Remove md4 caching and related ENABLE_BLAKE2B_HASHING feature flag

Announcements Deprecation
1

There is currently a feature flag in edx-platform that allows you to switch between md4 and blake2b hashing. This was added to allow operators to control the timing of the change from one hashing algorithm to another.

The proposal is here: [DEPR]: Remove md4 caching and related ENABLE_BLAKE2B_HASHING feature flag · Issue #36024 · openedx/edx-platform · GitHub

Acceptance date is: 2025-01-10T05:00:00Z

Removal target would be early April which would give folks 4 months more to transition.

2

I was over-eager and removed this feature flag before the acceptance date. If this causes any hardship, please let me know.