minor: upgrade Derivative dependency

Author: saghm

Cargo.toml

@@ -22,7 +22,7 @@ base64 = "0.11.0"
 bitflags = "1.1.0"
 bson = "0.14.1"
 chrono = "0.4.7"
-derivative = "1.0.2"
+derivative = "2.1.1"
 err-derive = "0.2.3"
 futures = "0.3.4"
 futures-intrusive = "0.3.0"