build(deps): bump secp256k1 from 0.20.2 to 0.20.3

Bumps [secp256k1](https://github.com/rust-bitcoin/rust-secp256k1) from 0.20.2 to 0.20.3.
- [Release notes](https://github.com/rust-bitcoin/rust-secp256k1/releases)
- [Changelog](https://github.com/rust-bitcoin/rust-secp256k1/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rust-bitcoin/rust-secp256k1/compare/secp256k1-0.20.2...secp256k1-0.20.3)

---
updated-dependencies:
- dependency-name: secp256k1
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Cargo.lock

@@ -2987,9 +2987,9 @@ dependencies = [
 
 [[package]]
 name = "secp256k1"
-version = "0.20.2"
+version = "0.20.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ee5070fdc6f26ca5be6dcfc3d07c76fdb974a63a8b246b459854274145f5a258"
+checksum = "97d03ceae636d0fed5bae6a7f4f664354c5f4fcedf6eef053fef17e49f837d0a"
 dependencies = [
  "secp256k1-sys",
  "serde",

zebra-chain/Cargo.toml

@@ -36,7 +36,7 @@ jubjub = "0.6.0"
 lazy_static = "1.4.0"
 rand_core = "0.6"
 ripemd160 = "0.9"
-secp256k1 = { version = "0.20.2", features = ["serde"] }
+secp256k1 = { version = "0.20.3", features = ["serde"] }
 serde = { version = "1", features = ["serde_derive", "rc"] }
 serde-big-array = "0.3.2"
 sha2 = { version = "0.9.5", features=["compress"] }