message: Update subxt to 0.2
diff: @@ -28,7 +28,7 @@ pwasm-utils = "0.11.0"
  parity-wasm = "0.40.2"
  cargo_metadata = "0.8.2"
  substrate-primitives = { git = "https://github.com/paritytech/substrate/", package = "substrate-primitives" }
  -subxt = { git = "https://github.com/paritytech/substrate-subxt/", branch = "v0.1", package = "substrate-subxt" }
  +subxt = { git = "https://github.com/paritytech/substrate-subxt/", branch = "v0.2", package = "substrate-subxt" }
  tokio = "0.1.21"
  url = "1.7"
  