README: distinguish announcements section (#7568)

README.md

@@ -5,7 +5,7 @@
 
 - [About](#about)
 - [Available Images](#available-images)
-- [Ongoing migrations](#ongoing-migrations)
+- [Announcements](#announcements)
 - [Image Definitions](#image-definitions)
 - [Image Releases](#image-releases)
 - [Software and Image Support](#software-and-image-support)
@@ -43,9 +43,9 @@ To build a VM machine from this repo's source, see the [instructions](docs/creat
 [macOS-10.15]: https://github.com/actions/runner-images/blob/main/images/macos/macos-10.15-Readme.md
 [self-hosted runners]: https://help.github.com/en/actions/hosting-your-own-runners
 
-## Ongoing migrations
+## Announcements
 
-There are no migrations in progress.
+See notable upcoming changes by viewing issues with the [Announcement](https://github.com/actions/runner-images/labels/Announcement) label.
 
 ## Image Definitions
 
@@ -79,7 +79,6 @@ latest 2 versions of an OS.
    - You can also track upcoming changes using the [awaiting-deployment](https://github.com/actions/runner-images/labels/awaiting-deployment) label.
 4. For high impact changes, we will post these in advance to the GitHub Changelog on our [blog](https://github.blog/changelog/) and on [twitter](https://twitter.com/GHchangelog).
    - Ex: breaking changes, GA or deprecation of images
-5. You can also view notable upcoming changes by viewing the [Announcement](https://github.com/actions/runner-images/labels/Announcement) label.
 
 *Cadence*