Fix style of opening statement (#15821)

web/app/components/base/chat/chat-with-history/chat-wrapper.tsx

           background={appData?.site.icon_background}
           imageUrl={appData?.site.icon_url}
         />
-        <Markdown className='!text-text-tertiary !body-2xl-regular' content={welcomeMessage.content} />
+        <div className='px-4 max-w-[768px]'>
+          <Markdown className='!text-text-tertiary !body-2xl-regular' content={welcomeMessage.content} />
+        </div>
       </div>
     )
   }, [appData?.site.icon, appData?.site.icon_background, appData?.site.icon_type, appData?.site.icon_url, chatList, collapsed, currentConversationId, inputsForms.length, respondingState])

web/app/components/base/chat/embedded-chatbot/chat-wrapper.tsx

           background={appData?.site.icon_background}
           imageUrl={appData?.site.icon_url}
         />
-        <Markdown className='!text-text-tertiary !body-2xl-regular' content={welcomeMessage.content} />
+        <div className='px-4 max-w-[768px]'>
+          <Markdown className='!text-text-tertiary !body-2xl-regular' content={welcomeMessage.content} />
+        </div>
       </div>
     )
   }, [appData?.site.icon, appData?.site.icon_background, appData?.site.icon_type, appData?.site.icon_url, chatList, collapsed, currentConversationId, inputsForms.length, respondingState])