JSON syntax update (#28193)

JSON syntax update

docs/sources/developers/plugins/legacy/data-sources.md

@@ -109,13 +109,13 @@ An array of:
         "text": "Time",
         "type": "time",
         "sort": true,
-        "desc": true,
+        "desc": true
       },
       {
-        "text": "mean",
+        "text": "mean"
       },
       {
-        "text": "sum",
+        "text": "sum"
       }
     ],
     "rows": [
@@ -128,7 +128,7 @@ An array of:
         1457425370000,
         1002.76215352,
         1002.76215352
-      ],
+      ]
     ],
     "type": "table"
   }