try to not run tests on master

Author: BjornFJohansson

.github/workflows/pydna_test_and_coverage_workflow.yml

@@ -3,6 +3,7 @@ on:
   push:
     branches:
       - '**'
+      - '!master'   # excludes master
     tags-ignore:
       - '*.*'
   pull_request: {}