Update platform.json

Author: Jason2866

platform.json

@@ -183,7 +183,7 @@
       "owner": "pioarduino",
       "package-version": "1.13.1",
       "version": "https://github.com/pioarduino/registry/releases/download/0.0.1/ninja-1.13.1.zip"
-    }
+    },
     "tool-scons": {
       "type": "tool",
       "optional": true,