fix: Correct double callback in persistent store wrapper. (#240)

Author: kinyoklion

packages/shared/sdk-server/src/store/PersistentDataStoreWrapper.ts

@@ -166,6 +166,7 @@ export default class PersistentDataStoreWrapper implements LDFeatureStore {
         const value = deserialize(persistKind, descriptor);
         this.itemCache?.set(cacheKey(kind, key), value);
         callback(itemIfNotDeleted(value));
+        return;
       }
       callback(null);
     });