fix(json-schema-2020-12): fix rendering of items keywords (#8674)

As JSON Schema 2020-12 can be represented as
a Boolean Schema, different keyword detection
needs to be used.

Refs #8513

src/core/plugins/json-schema-2020-12/fn.js

@@ -151,7 +151,7 @@ export const isExpandable = (schema) => {
     fn.hasKeyword(schema, "else") ||
     schema?.dependentSchemas ||
     schema?.prefixItems ||
-    schema?.items ||
+    fn.hasKeyword(schema, "items") ||
     fn.hasKeyword(schema, "contains") ||
     schema?.properties ||
     schema?.patternProperties ||