[docs] End v6 blogpost notification (#39879)

docs/notifications.json

@@ -4,11 +4,6 @@
     "title": "<b>Check out Base UI today</b> 💥",
     "text": "Love Material UI, but don't need Material Design? Try Base UI, the new \"unstyled\" alternative. <a style=\"color: inherit;\" data-ga-event-category=\"Blog\" data-ga-event-action=\"notification\" data-ga-event-label=\"introducing-base-ui\" href=\"/blog/introducing-base-ui/\">Read more in this announcement</a>."
   },
-  {
-    "id": 74,
-    "title": "<b>Introducing MUI X v6.0.0</b>",
-    "text": "<a style=\"color: inherit;\" data-ga-event-category=\"Blog\" data-ga-event-action=\"notification\" data-ga-event-label=\"mui-x-v6\" href=\"/blog/mui-x-v6/\">Explore</a> what's new and what's next in the new stable version of the advanced components."
-  },
   {
     "id": 75,
     "title": "<b>Try the new time picker UI now</b>",
@@ -23,5 +18,10 @@
     "id": 77,
     "title": "<b>MUI Toolpad is now in Beta</b>",
     "text": "Import in your codebase, connect to datasources and build your UI in minutes! Read our <a style=\"color: inherit;\" data-ga-event-category=\"Announcement\" data-ga-event-action=\"notification\" data-ga-event-label=\"mui-toolpad-introduce-beta\" href=\"https://mui.com/blog/2023-toolpad-beta-announcement/\"> Beta announcement</a>, try toolpad and share your feedback."
+  },
+  {
+    "id": 78,
+    "title": "<b>MUI X v6.18.x and the latest improvements before the next major</b>",
+    "text": "New stable components, polished features, better performance and more. Check out the details in our <a style=\"color: inherit;\" data-ga-event-category=\"Announcement\" data-ga-event-action=\"notification\" data-ga-event-label=\"mui-x-end-v6\" href=\"https://mui.com/blog/mui-x-end-v6-features/\">recent blog post</a>."
   }
 ]