Disable Azure pipelines build for docs-master too.

.ci/azure-pipelines.yml

@@ -3,6 +3,11 @@
 # Add steps that analyze code, save the dist with the build record, publish to a PyPI-compatible index, and more:
 # https://docs.microsoft.com/azure/devops/pipelines/languages/python
 
+trigger:
+  branches:
+    exclude:
+    - docs-master
+
 jobs:
 
 - job: Mac