Fix VLC task design (#238)

* fix: fix multiapp tasks

* fix: update instructions for VLC evaluation examples

---------

Co-authored-by: adlsdztony <zzl0712@connect.hku.hk>

evaluation_examples/examples/multi_apps/5990457f-2adb-467b-a4af-5c857c92d762.json

@@ -9,6 +9,7 @@
       "parameters": {
         "command": [
           "google-chrome",
+          "--proxy-server=http://127.0.0.1:18888",
           "--remote-debugging-port=1337"
         ]
       }