Update secp256k1 requirement from 0.27.0 to 0.28.0

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
...

Signed-off-by: dependabot[bot] <[email protected]>

Cargo.toml

@@ -26,7 +26,7 @@ blake2 = "0.10.6"
 ethereum-types = "0.14.0"
 itertools = "0.12.0"
 tiny-keccak = { version = "2.0.0", features = ["keccak"] }
-secp256k1 = { version = "0.27.0", features = [ "recovery" ] }
+secp256k1 = { version = "0.28.0", features = [ "recovery" ] }
 tiny-bip39 = "1.0.0"
 rustc-hex = "2.1.0"
 open-fastrlp = { version = "0.1.4", features = ["std", "ethereum-types"] }