Add missing } to updateArticle code sample (#6924)

Before this change the example curl command returns 400 bad request with an appropriate API key and article ID.

After this change the example curl command does not return error 400 bad request.

docs/api_v0.yml

@@ -1890,7 +1890,7 @@ paths:
           source: |
             curl -X PUT -H "Content-Type: application/json" \
               -H "api-key: API_KEY" \
-              -d '{"article":{"title":"Title"}' \
+              -d '{"article":{"title":"Title"}}' \
               https://dev.to/api/articles/{id}
 
   /articles/me: