Merge branch 'refactor/substrate-state-machine-generic' of...

Merge branch 'refactor/substrate-state-machine-generic' of github.com:paritytech/polkadot into refactor/substrate-state-machine-generic

* 'refactor/substrate-state-machine-generic' of github.com:paritytech/polkadot:
  Update Cargo.lock
  Remove safe-mix (#521)