Add generated annotation to Authentication.mustache

Author: reitzmichnicht

modules/openapi-generator/src/main/resources/Java/auth/Authentication.mustache

@@ -7,6 +7,7 @@ import {{invokerPackage}}.Pair;
 import java.util.Map;
 import java.util.List;
 
+{{>generatedAnnotation}}
 public interface Authentication {
     /**
      * Apply authentication settings to header and query params.