chore: Update dependency versions and sources in Cargo.toml (#338)

* chore: Update dependency versions and sources in Cargo.toml

- Updated the version of `bellpepper-core` dependency to `0.4.0`.
- Changed the repository source for `bellpepper` and `neptune` dependencies from `lurk-lab` to `huitseeker`.
- Transitioned `neptune` dependency's branch from "dev" to "switch-bellpepper-dependency".

* point neptune & bellpepper back to lurk-lab@dev

Cargo.toml

@@ -12,7 +12,7 @@ keywords = ["zkSNARKs", "cryptography", "proofs"]
 rust-version="1.71.0"
 
 [dependencies]
-bellpepper-core = { git="https://github.com/lurk-lab/bellpepper", branch="dev", default-features = false }
+bellpepper-core = { version = "0.4.0", default-features = false }
 bellpepper = { git="https://github.com/lurk-lab/bellpepper", branch="dev", default-features = false }
 ff = { version = "0.13.0", features = ["derive"] }
 digest = "0.10"