simplify additionalItems validation flow (#1256)

Author: Oz-er

src/main/java/com/networknt/schema/keyword/ItemsLegacyValidator.java

@@ -186,9 +186,7 @@ private boolean doValidate(ExecutionContext executionContext, int i, JsonNode no
                         executionContext.evaluationPathAddLast("items");
                     }
                 } else if (this.additionalItems != null) {
-                    if (this.additionalItems) {
-//                        evaluatedItems.add(path);
-                    } else {
+                    if (!this.additionalItems) {
                         // no additional item allowed, return error
                         executionContext.evaluationPathRemoveLast(); // remove items
                         executionContext.evaluationPathAddLast("additionalItems");