Fix minor documentation error (#5851)

Adding a required `,` in the sample JSON

docs/content/development/extensions-contrib/time-min-max.md

@@ -57,7 +57,7 @@ To query for results, the same aggregators "timeMin" and "timeMax" is used.
     {
       "type": "count",
       "name": "count"
-    }
+    },
     {
       "type": "timeMin",
       "name": "<output_name of timeMin>",
@@ -82,4 +82,4 @@ Then, result has min and max of timestamp, which is finer than query granularity
 2015-07-28T00:00:00.000Z B 2 2015-07-28T04:00:00.000Z 2015-07-28T06:00:00.000Z
 2015-07-29T00:00:00.000Z A 2 2015-07-29T03:00:00.000Z 2015-07-29T04:00:00.000Z
 2015-07-29T00:00:00.000Z C 2 2015-07-29T01:00:00.000Z 2015-07-29T02:00:00.000Z
-```
+```