Do not remove schemas with only a default value form allOf schemas

A schema with only a default was treated as "meta data only" this caused it to be removed from an allOf schema causing the default value to be lost

Author: WellingR

modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/ModelUtils.java

@@ -2358,7 +2358,8 @@ public static boolean isMetadataOnlySchema(Schema schema) {
                 schema.getContains() != null ||
                 schema.get$dynamicAnchor() != null ||
                 schema.get$anchor() != null ||
-                schema.getContentSchema() != null;
+                schema.getContentSchema() != null ||
+                schema.getDefault() != null;
     }