Update secp256k1 requirement from 0.28 to 0.29

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

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

Cargo.toml

@@ -13,7 +13,7 @@ version = "0.10.0"
 zeroize = "1.0.0"
 rand = "0.8.0"
 rustc-hex = "2.0.1"
-secp256k1 = { version = "0.28", optional = true, features = ["recovery"] }
+secp256k1 = { version = "0.29", optional = true, features = ["recovery"] }
 serde = { version = "1.0", features = ["derive"]}
 
 # Libraries for for pure-rust crypto