fix attribute expiration_date_warned

Author: wurstbrot

src/main/java/io/securecodebox/persistence/defectdojo/models/RiskAcceptance.java

@@ -54,9 +54,6 @@ public class RiskAcceptance extends DefectDojoModel {
   @JsonProperty
   String expiration_date;
 
-  @JsonProperty
-  LocalDateTime expiration_date_warned;
-
   @JsonProperty
   Boolean expiration_date_handled;