Update push_build_and_test.yml

Author: soernt

.github/workflows/push_build_and_test.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-20.04
     defaults:
       run:
-        working-directory: ./app
+        working-directory: ./source
 
     steps:
     - uses: actions/checkout@v2