Bump sha2 from 0.9.5 to 0.9.6

Bumps [sha2](https://github.com/RustCrypto/hashes) from 0.9.5 to 0.9.6.
- [Release notes](https://github.com/RustCrypto/hashes/releases)
- [Commits](RustCrypto/hashes@sha2-v0.9.5...sha2-v0.9.6)

---
updated-dependencies:
- dependency-name: sha2
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

zebra-chain/Cargo.toml

@@ -40,7 +40,7 @@ ripemd160 = "0.9"
 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"] }
+sha2 = { version = "0.9.6", features=["compress"] }
 subtle = "2.4"
 thiserror = "1"
 uint = "0.9.1"