fix(grumbles): bump rustc-hex = 2

Author: niklasad1

Cargo.lock

@@ -90,7 +90,7 @@ macros = { path = "../util/macros" }
 null-engine = { path = "./engines/null-engine" }
 parity-runtime = { path = "../util/runtime" }
 rlp_compress = { path = "../util/rlp-compress" }
-rustc-hex = "1"
+rustc-hex = "2"
 serde_json = "1.0"
 stats = { path = "../util/stats" }
 pod = { path = "pod" }