Updated: Misssing comma

Co-authored-by: krivard <[email protected]>

Author: vishakha1812

google_health/tests/params.json.template

@@ -4,6 +4,6 @@
   "cache_dir": "../cache",
   "start_date": "2020-02-11",
   "end_date": "2020-04-30",
-  "ght_key": ""
+  "ght_key": "",
   "wip_signal": ""
 }