Add missing comma in test/README.md.

test/README.md

@@ -1,7 +1,7 @@
 There are unfortunately no automated tests for releasehealth-bot, but
 there is a very simple test server that acts like a Bugzilla
 instance.  It requires flask (`pip install flask`) and a local
-JSON-encoded file, `query_values.json` that contains fake data.  The
+JSON-encoded file, `query_values.json`, that contains fake data.  The
 file is loaded fresh on every query, so you can change the values to
 prompt a test releasehealth-bot to issue updates.  An example file,
 `query_values.json.example`, is included, though the versions will have