Fix example JSON so that it's valid

I got bit by copy/pasting this blindly in the OPA playground

authorization/overview.mdx

@@ -77,7 +77,7 @@ Here is an example of the `input.authentication.metadata` field for a request au
 ```json
 {
     "io.flipt.auth.email": "[email protected]",
-    "io.flipt.auth.name": "John Doe"
+    "io.flipt.auth.name": "John Doe",
     "io.flipt.auth.claims": {
         "roles": ["admin", "viewer"]
     }