Release v1.8.1

Docker reference: paritytech/substrate-relay:v1.8.1

Bundled Chain Versions:

Rococo: 1_016_001;
Westend: 1_016_001;
Kusama: 1_002_004;
Polkadot: 1_003_003;
Rococo Bridge Hub: 1_016_001;
Westend Bridge Hub: 1_016_001;
Kusama Bridge Hub: 1_004_000;
Polkadot Bridge Hub: 1_004_000;
Rococo Bulletin: not supported yet;
Polkadot Bulletin: not supported yet.

What's Changed

• updating relay-clients versions wt runtimes v1.4.0 by @rosarp in #3128

Full Changelog: v1.8.0...v1.8.1