ci: change app id to vars, remove deploy stage workflow (#365)

Co-authored-by: kim <kim.phanhoang@epfl.ch>

Author: pyphilia

.github/workflows/deploy-prod.yml

@@ -46,7 +46,7 @@ jobs:
         with:
           # Replace input build-folder or version if needed
           build-folder: 'build'
-          graasp-app-id: ${{ secrets.APP_ID }}
+          graasp-app-id: ${{ vars.APP_ID }}
           version: 'latest'
           aws-access-key-id: ${{ secrets.AWS_ACCESS_KEY_ID_PROD }}
           aws-secret-access-key: ${{ secrets.AWS_SECRET_ACCESS_KEY_PROD }}