Fix namespaces getlist processor when cache_db is active (#16681)

### What does it do?
Makes sure the code doesn't try to cache this specific query.

### Why is it needed?
When `cache_db` is active, the processor throws an error (`Code: 0
communication failure`).

### How to test
* Set the system setting `cache_db` to `Yes`
* Make sure that on the system settings page
(`manager/?a=system/settings`), the dropdown "Filter by namespace..."
displays the list of namespaces.

### Related issue(s)/PR(s)
Resolves #16674

core/src/Revolution/Processors/Workspace/PackageNamespace/GetList.php

@@ -114,7 +114,7 @@ public function prepareQueryBeforeCount(xPDOQuery $c)
                     if ($foreignKeyWhere) {
                         $nsSubquery->where($foreignKeyWhere);
                     }
-                    $namespaces = $this->modx->getObject($settingsClass, $nsSubquery)->get('namespaces');
+                    $namespaces = $this->modx->getObject($settingsClass, $nsSubquery, false)->get('namespaces');
 
                     $c->where(
                         "`{$c->getAlias()}`.`name` IN (\"{$namespaces}\")"