chore(readme): update links (ublue-os#684)

Co-authored-by: Jorge O. Castro <[email protected]>

README.md

@@ -17,8 +17,8 @@ A familiar(ish) Ubuntu desktop for Fedora Silverblue. It strives to cover these
 
 # Documentation
 
-1. [Bluefin](https://universal-blue.org/images/bluefin/)
+1. [Bluefin](http://universal-blue.discourse.group/t/introduction-to-bluefin/41)
 2. [Discussions and Announcements](https://universal-blue.discourse.group/c/bluefin/6) - strongly recommended!
-3. [Developer Experience Edition](https://universal-blue.org/images/bluefin/developer-experience)
-4. [Administrator's Guide](https://universal-blue.discourse.group/docs?topic=40)
+3. [Developer Experience Edition](http://universal-blue.discourse.group/t/bluefin-dx-the-bluefin-developer-experience/39)
+4. [Administrator's Guide](http://universal-blue.discourse.group/t/bluefin-administrators-guide/40)
 5. [Framework Images](https://universal-blue.org/images/framework/)