[6.x] Fix custom entry class test artifact (#14356)

Author: jasonvarga

tests/Stache/Repositories/EntryRepositoryTest.php

@@ -275,6 +275,8 @@ public function it_gets_custom_entry_class()
             ->collection(Collection::findByHandle('custom_class'))
             ->slug('custom');
 
+        $this->unlinkAfter($this->directory.'/custom_class/custom.md');
+
         $this->repo->save($temp);
         $entry = $this->repo->find('custom');