build(deps): Update secp256k1 requirement from 0.27.0 to 0.28.0 (#79)

Updates the requirements on [secp256k1](https://github.com/rust-bitcoin/rust-secp256k1) to permit the latest version.
- [Changelog](https://github.com/rust-bitcoin/rust-secp256k1/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rust-bitcoin/rust-secp256k1/commits/secp256k1-0.28.0)

---
updated-dependencies:
- dependency-name: secp256k1
  dependency-type: direct:production
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

crates/avalanche-types/Cargo.toml

@@ -47,7 +47,7 @@ zerocopy = "0.6.3"
 zeroize = "1.6.0" # for "BLS
 
 # [OPTIONAL] for "libsecp256k1"
-secp256k1 = { version = "0.27.0", features = ["global-context", "rand-std", "recovery"], optional = true } # https://crates.io/crates/secp256k1
+secp256k1 = { version = "0.28.0", features = ["global-context", "rand-std", "recovery"], optional = true } # https://crates.io/crates/secp256k1
 
 # [OPTIONAL] for "kms_aws"
 aws-manager = { version = "0.30.2", features = ["kms"], optional = true } # https://github.com/gyuho/aws-manager/tags