downgraded ubuntu for runner stage 'deploy-function'

Author: hvalfangst

.github/workflows/deploy_to_azure.yml

@@ -45,7 +45,7 @@ jobs:
             !venv/
 
   deploy-function:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-18.04
     needs: build-function
     permissions:
       id-token: write