Adapt ActionStatus timestamp doc (#2130)

Co-authored-by: vasilchev <vasil.ilchev@bosch.com>

hawkbit-ddi/hawkbit-ddi-api/src/main/java/org/eclipse/hawkbit/ddi/json/model/DdiActionFeedback.java

@@ -47,7 +47,7 @@ import lombok.Data;
 @JsonIgnoreProperties(ignoreUnknown = true)
 public class DdiActionFeedback {
 
-    @Schema(description = "Timestamp of the action in milliseconds since epoch", example = "1627997501890")
+    @Schema(description = "Timestamp (in milliseconds) when this status change occurred on Device.", example = "1627997501890")
     private final Long timestamp;
 
     @NotNull