azure pipelines: fix branch patterns to support 1.x release branches

I would like to use the same pattern rule as github actions uses:

'[0-9]+.[0-9]+'

But azure pipelines doesn't document what the syntax here is, and it
scares me that perhaps the reason we didn't already do this is because
it doesn't work at all.

azure-pipelines.yml

@@ -19,7 +19,7 @@ trigger:
     include:
     - 'master'
     # Release branches
-    - '0.*'
+    - '1.*'
   paths:
     include:
       - 'mesonbuild'