Fix: Update removes many to many relations (#376)

Calling $this->update in restoreRevision method made a call to syncPivot method witch removed all related records.

Author: Ghitu

src/PanelTraits/ViewsAndRestoresRevisions.php

@@ -47,7 +47,7 @@ public function restoreRevision($id, $revisionId)
         $revision = Revision::findOrFail($revisionId);
 
         // Update the revisioned field with the old value
-        $this->update($entry->getKey(), [$revision->key => $revision->old_value]);
+        $entry->update([$revision->key => $revision->old_value]);
 
         // Reload the entry so we have the latest revisions
         $entry = $this->getEntry($id);