fix gcp domain use in app deployment

example_app/.drone-kube/deployment.yml

@@ -60,7 +60,7 @@ spec:
   entryPoints:
     - https
   routes:
-    - match: Host(`${INSTANCE_NAME}-${APP_NAME}.${APP_DOMAIN}`)
+    - match: Host(`${INSTANCE_NAME}-${APP_NAME}.${GCP_DOMAIN}`)
       kind: Rule
       services:
         - namespace: ${APP_NAME}
@@ -69,4 +69,4 @@ spec:
   tls:
     certResolver: letsencrypt
     domains:
-      - main: "*.${APP_DOMAIN}"
+      - main: "*.${GCP_DOMAIN}"