Backport PR #42583: CI: auto-cancel Azure builds in PR (#42641)

Co-authored-by: Fangchen Li <[email protected]>

Author: meeseeksmachine

azure-pipelines.yml

@@ -9,9 +9,11 @@ trigger:
     - 'doc/*'
 
 pr:
-- master
-- 1.2.x
-- 1.3.x
+  autoCancel: true
+  branches:
+    include:
+    - master
+    - 1.3.x
 
 variables:
   PYTEST_WORKERS: auto