Bump structopt from 0.3.11 to 0.3.12 (#42)

bridges/bin/node/node/Cargo.toml

@@ -13,7 +13,7 @@ name = "bridge-node"
 [dependencies]
 futures = "0.3.1"
 log = "0.4.8"
-structopt = "0.3.8"
+structopt = "0.3.12"
 bridge-node-runtime = { version = "0.1.0", path = "../runtime" }
 sp-bridge-eth-poa = { version = "0.1.0", path = "../../../primitives/ethereum-poa" }