Update doughnut-rs version for codec and schnorrkel compatibility

Author: jordy25519

Cargo.lock

@@ -22,7 +22,7 @@ log = { version = "0.4.8", optional = true }
 paste = "0.1.6"
 rand = { version = "0.7.2", optional = true }
 impl-trait-for-tuples = "0.1.3"
-doughnut = { package = "doughnut_rs", branch = "0.3.0", git = "https://github.com/cennznet/doughnut-rs", default-features = false }
+doughnut = { package = "doughnut_rs", branch = "0.3.1", git = "https://github.com/cennznet/doughnut-rs", default-features = false }
 sp-inherents = { version = "2.0.0-alpha.2", default-features = false, path = "../inherents" }
 parity-util-mem = { version = "0.5.1", default-features = false, features = ["primitive-types"] }