Remove unused UI schema field

Author: sd109

chart/azimuth-ui.schema.yaml

@@ -9,7 +9,6 @@ controls:
     type: TextControl
   /ui/appSettings/page_title:
     type: TextControl
-    placeholder: "Large Language Model"
   /ui/appSettings/llm_max_tokens:
     type: NumberControl
   /ui/appSettings/llm_temperature: