doc: update saas app_desc.yaml (#8277)

--story=120799474

Author: wcy00000000000000

docs/smart/web/app_desc.yaml

@@ -25,6 +25,12 @@ modules:
           replicas: 1
           resQuotaPlan: default
           targetPort: 80
+          services:
+            - name: web
+              exposedType:
+                name: bk/http
+              targetPort: 80
+              port: 80
       configuration:
         env:
         - name: "GO_INSTALL_PACKAGE_SPEC"