Function pallet_session::historical::offchain::prune_older_than

pub fn prune_older_than<T: Config>(first_to_keep: SessionIndex)

Attempt to prune anything that is older than first_to_keep session index.

Due to re-organisation it could be that the first_to_keep might be less than the stored one, in which case the conservative choice is made to keep records up to the one that is the lesser.