CI: do not include */ci branches in PR builds

Align Azure Pipelines with GitHub Actions.
diff --git a/.azure-pipelines.yml b/.azure-pipelines.yml
index 77a47ab..29f278c 100644
--- a/.azure-pipelines.yml
+++ b/.azure-pipelines.yml
@@ -34,7 +34,6 @@
   branches:
     include:
     - 'master'
-    - '*/ci'
 
 stages: