Improve documentation

Link

https://supabase.com/docs/reference/javascript/upsert

Describe the problem

The response of the Upserting into tables with constraints example is false.
The correct one is :
{ "data": [ { "id": 42, "handle": "saoirse", "display_name": "Saoirse" } ] }

Describe the improvement

Just change the current response with the correct one.