No need for memento hack (#234450)

MSAL node made `clearCache` synchronous :tada: so we can safely depend on it for clearing the cache.

> Context: The default behavior of MSAL's internal cache is that it is a union with what's in the persistant cache (secret storage) but what _we_ want is that secret storage is the source of truth, so every time we receive an update to secret storage, we clear the in-memory cache to get the data from the persistant cache.

Also bumps msal-node-extensions while we're at it.