add MySQL 0.34 support (#327)

Author: oscartbeaumont

refinery_core/Cargo.toml

@@ -33,7 +33,7 @@ rusqlite = { version = ">= 0.23, <= 0.31", optional = true }
 postgres = { version = ">=0.17, <= 0.19", optional = true }
 tokio-postgres = { version = ">= 0.5, <= 0.7", optional = true }
 mysql = { version = ">= 21.0.0, <= 24", optional = true, default-features = false, features = ["minimal"] }
-mysql_async = { version = ">= 0.28, <= 0.33", optional = true, default-features = false, features = ["minimal"] }
+mysql_async = { version = ">= 0.28, <= 0.34", optional = true, default-features = false, features = ["minimal"] }
 tiberius = { version = ">= 0.7, <= 0.12", optional = true, default-features = false }
 tokio = { version = "1.0", optional = true }
 futures = { version = "0.3.16", optional = true, features = ["async-await"] }