This release upgrades the Kintsugi from 1.7.3 to 1.8.1

Major changes

• Upgrade polkadot dependency to 0.9.17
• Fix difficulty check bug in btc-relay
• Fix stack overflow in democracy due to missing decode limit in do_enact_proposal
• Don't charge a tx fee for execute_redeem

Release notes

• https://github.com/interlay/interbtc/releases/tag/1.8.1
• https://github.com/interlay/interbtc/releases/tag/1.8.0
• https://github.com/interlay/interbtc/releases/tag/1.7.4

Code changes

https://github.com/interlay/interbtc/compare/1.7.3...1.8.1