Double check redundant validations were removed from qbft

[diegomrsantos]

Stateless validation (that doesn't depend on the current consensus state) is being moved to the message validator. This issue is to double-check we didn't leave redundant checks in qbft.

[diegomrsantos]

Qbft logic also needs to be checked, like mentioned here https://github.com/sigp/anchor/pull/191/files#r2014993628