Issue #3466522 by jwilson3: Support PHP 8.3

Closes #3466522

rivet.theme

@@ -593,7 +593,7 @@ function _rivet_get_entity_cache_id() {
     if ($param instanceof EntityInterface) {
       $entity_type = $param->getEntityTypeId();
       $entity_id = $param->id();
-      return "${entity_type}:${entity_id}";
+      return "{$entity_type}:{$entity_id}";
     }
   }
 }