fix version in documentation

Author: Jan Seidl

README.md

@@ -192,7 +192,7 @@ unwrap all erros, you should use `WrappedErrors()` instead
 
     fmt.Println(errors.Unwrap(err)) # "original error" is printed
 
-added in version 4.1.0
+added in version 4.2.0
 
 #### func (Error) WrappedErrors
 

retry.go

@@ -222,7 +222,7 @@ when you need unwrap all erros, you should use `WrappedErrors()` instead
 
 	fmt.Println(errors.Unwrap(err)) # "original error" is printed
 
-added in version 4.1.0
+added in version 4.2.0
 */
 func (e Error) Unwrap() error {
 	return e[len(e)-1]