[doc] add a hint about new scheduler triggering to release notes

ReleaseNotes-2.3

@@ -115,6 +115,10 @@ Changes:
     source links, this means the generated files become visible with expand=1 parameter.
   - The state of the service is visible via serviceinfo element in package file list.
 
+* The scheduler is excluding the link information on calculating rebuilds. This means it triggers
+  only builds when the merged source has changed.
+  NOTE: as a side effect all linked packages will get rebuild due to changed md5sum after 2.3 update.
+
 * The backend is only accepting write access from the localhost by default. Build results can be
   still delivered from any host. This can be changed in BSConfig.pm