Mesh 2149/staking update migrations

[HenriqueNogara]

changelog

data migration

• pallet_staking
  • The following Storage have been removed: SnapshotValidators, SnapshotNominators, QueuedElected, QueuedScore, EraElectionStatus, IsCurrentSessionFinal, HistoryDepth, MinimumBondThreshold, EarliestUnappliedSlash;
  • The following storage have changed types: Validators, Nominators;