refactor: Update optional properties input in schema (#2754)

Author: jnsdls

.changeset/pink-bobcats-greet.md

@@ -0,0 +1,5 @@
+---
+"@thirdweb-dev/sdk": patch
+---
+
+handle `[[{}]]` values for `properties` / `attributes` fields of NFTs

legacy_packages/sdk/src/core/schema/properties.ts

@@ -9,6 +9,6 @@ const PropertiesInput = /* @__PURE__ */ (() =>
  */
 export const OptionalPropertiesInput = /* @__PURE__ */ (() =>
   z
-    .union([z.array(PropertiesInput), PropertiesInput])
+    .union([z.array(z.array(PropertiesInput)).transform(i => i.flat()), z.array(PropertiesInput), PropertiesInput])
     .optional()
     .nullable())();