Update CI schedule.

Author: felixfontein

.azure-pipelines/azure-pipelines.yml

@@ -29,14 +29,14 @@ schedules:
     always: true
     branches:
       include:
+        - stable-11
         - stable-10
-        - stable-9
   - cron: 0 11 * * 0
     displayName: Weekly (old stable branches)
     always: true
     branches:
       include:
-        - stable-8
+        - stable-9
 
 variables:
   - name: checkoutPath