refactor: remove unused section title styles and update class name for consistency

apps/app/src/features/openai/client/components/AiAssistant/Sidebar/AiAssistantList.module.scss

@@ -9,13 +9,6 @@
   }
 }
 
-.ai-assistant-list :global {
-  .grw-assistant-section-title {
-    font-size: 14px;
-  }
-}
-
-
 .ai-assistant-list :global {
   .list-group-item {
     height: 40px;

apps/app/src/features/openai/client/components/AiAssistant/Sidebar/AiAssistantList.tsx

@@ -312,7 +312,7 @@ export const AiAssistantList: React.FC<AiAssistantListProps> = ({
         aria-expanded={!isCollapsed}
         onClick={toggleCollapse}
       >
-        <h3 className="fw-bold grw-assistant-section-title mb-0 me-1">
+        <h3 className="grw-ai-assistant-substance-header fw-bold mb-0 me-1">
           {t(`ai_assistant_list.${isTeamAssistant ? 'team' : 'my'}_assistants`)}
         </h3>
         <span