Unlock once_cell version (#22)

* Unlock once_cell version

* change once_cell version to 1.14

Author: chrislearn

Cargo.toml

@@ -20,8 +20,7 @@ futures-channel = "0.3"
 futures-util = { version = "0.3", default-features = false }
 http = "0.2"
 
-# Necessary to overcome msrv check of rust 1.49, as 1.15.0 failed
-once_cell = "=1.14"
+once_cell = "1.14"
 
 pin-project-lite = "0.2.4"
 socket2 = "0.4"