Remove async recursion

Greatly increases safety as well by ensuring only one message is 
processed at once.

substrate/tendermint/Cargo.toml

@@ -10,6 +10,5 @@ edition = "2021"
 [dependencies]
 parity-scale-codec = { version = "3.2", features = ["derive"] }
 
-async-recursion = "1.0"
 async-trait = "0.1"
 tokio = { version = "1", features = ["macros", "rt", "sync"] }