Backport schedule in yaml

I'm not sure it's needed, but let's try it: Add the scheduled
builds on PHP-7.4 and PHP-8.0 as well, rather than just master.

Author: nikic

azure-pipelines.yml

@@ -11,6 +11,14 @@ trigger:
       - UPGRADING
       - UPGRADING.INTERNALS
 
+schedules:
+  - cron: "0 1 * * *"
+    displayName: Nightly build
+    branches:
+      include:
+        - PHP-7.4
+        - master
+
 jobs:
   - template: azure/job.yml
     parameters: