[docs] Add notification for MUI X v7 blog post (#41587) (#41605)

Co-authored-by: Danilo Leal <67129314+danilo-leal@users.noreply.github.com>

docs/notifications.json

@@ -15,8 +15,8 @@
     "text": "Take a few minutes to share your feedback and expectations in the <a style=\"color: inherit;\" data-ga-event-category=\"Announcement\" data-ga-event-action=\"notification\" data-ga-event-label=\"mui-survey\" href=\"https://tally.so/r/3Ex4PN?source=docs-notification\">Developer Survey</a>."
   },
   {
-    "id": 80,
-    "title": "MUI X v7.0.0-beta.0",
-    "text": "Featuring new components and multiple enhancements for both developers and end-users. Discover all the specifics in the <a style=\"color: inherit;\" data-ga-event-category=\"Announcement\" data-ga-event-action=\"notification\" data-ga-event-label=\"mui-x-v7-beta\" href=\"https://mui.com/blog/mui-x-v7-beta/\">announcement blog post</a>."
+    "id": 81,
+    "title": "Introducing MUI X v7",
+    "text": "This new version is packed with new components, exciting features, improved usability, and developer experience. Check out the <a style=\"color: inherit;\" data-ga-event-category=\"Announcement\" data-ga-event-action=\"notification\" data-ga-event-label=\"mui-x-v7\" href=\"https://mui.com/blog/mui-x-v7/\">announcement blog post</a>."
   }
 ]