Change CI workflow to use master branch

Author: leric2

.github/workflows/CI_tests.yaml

@@ -8,7 +8,7 @@ on:
     - cron: '40 14 * * *'
   push:
     branches:
-      - meteoswiss-dev
+      - master
   pull_request:
   workflow_dispatch:
 
@@ -22,7 +22,7 @@ jobs:
     steps:
       - uses: actions/checkout@v3
         with:
-          ref: meteoswiss-dev
+          ref: master
       - name: Set up python ${{ matrix.python-version }}
         uses: actions/setup-python@v4
         with: