chore: remove django settings module from devcontainer config (ietf-tools#3673)

Author: NGPixel

.devcontainer/docker-compose.extend.yml

@@ -4,11 +4,10 @@ services:
     app:
         environment:
             EDITOR_VSCODE: 1
-            DJANGO_SETTINGS_MODULE: settings_local_sqlitetest
         volumes:
             - .:/workspace
             - /workspace/node_modules
             - /workspace/.parcel-cache
             - /workspace/__pycache__
         # Runs app on the same network as the database container, allows "forwardPorts" in devcontainer.json function.
-        network_mode: service:db
+        network_mode: service:db