Revert "client: defensive against getting stale alloc updates"

[notnoop]

Reverts #5906

This reverts a defensive check against leaders violating a monotonic consistency where leaders returned stale data. Well, now this can happen due to snapshot restore to a previous time.

Note that we haven't observed this issue in any setup outside single dev instance clusters, and the actual underlying issue has been addressed in #5911 .

I have considered adding a more sophisticated way to have clients detect if state got reverted manually but decided against it, because the underlying issues were already addressed and I worry that any additional sophisticated checks will be additional complexity that can have more damaging effects. Sample abandoned consideration: if a client notices a rollback of index, wait for N seconds before trusting value and killing local allocs; have server RPC return overall server index and have client compare the two if there is a discrepancy.

[github-actions]

I'm going to lock this pull request because it has been closed for 120 days ⏳. This helps our maintainers find and focus on the active contributions.
If you have found a problem that seems related to this change, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.