Contracts: Stabilize APIs (#3384)
Remove `#[unstable]` on `call_v2`, `instantiate_v2`, `lock_delegate_dependency` and `unlock_delegate_dependency`. See ink! integrations: - call_v2: https://github.com/paritytech/ink/pull/2077 - instantiate_v2: <TODO> - lock/unlock dependency: https://github.com/paritytech/ink/pull/2076