text: Title: Storage upsert docs are incorrect
  Body: **Describe the bug**
  The docs on how to control storage upserts are out of date. 
  
  The docs say that an `upsert` header is allowed
  https://supabase.com/docs/reference/python/storage-from-update
  
  But the underlying storage3 lib accepts an `x-upsert` param not an `upsert`
  https://github.com/supabase-community/storage-py/blob/main/storage3/constants.py#L12
  
  cc @olirice 