CI: reduce test cases

- GH: Remove python 3.7 on github actions test.
- Azure: Only run on master and rel-* branch.

Signed-off-by: Hiroshi Miura <miurahr@linux.com>

azure-pipelines.yml

@@ -1,3 +1,9 @@
+trigger:
+  branches:
+    include:
+    - master
+    - rel-*
+
 jobs:
 - job: MatricesGenerator
   displayName: Matrices Generator