relayer: remove RelayV2 init code

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CKB has launched CKB 2023 hardfork, so we can remove Relayer V2 init related code.

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In test-wasm CI job, it install wasm-pack by cargo install wasm-pack, but wasm-pack failed to be built on rust 1.85.0.

We can avoid that by using cargo-binstall to install wasm-pack by cargo binstall wasm-pack. 721e5ac

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Request @quake @driftluo to review.

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@quake Rebased onto develop. Ready to merge.