Fix integration test workflow (#1439)

We want to trigger integration tests on every branch
except master branch. Got this from stackoverflow[1]

[1] https://stackoverflow.com/a/57903434

.github/workflows/branch-integration-tests.yaml

@@ -5,7 +5,10 @@ name: branch-integration-tests
 on:
   push:
     branches:
-      - '*'
+      - '*'         # matches every branch that doesn't contain a '/'
+      - '*/*'       # matches every branch containing a single '/'
+      - '**'        # matches every branch
+      - '!master'   # excludes master
 
 jobs:
   integration-tests: