Don't replace selected columns with "..."

[Lauréline Guérin]

These 2 queries produce the same result:

list(Author.objects.all())
list(Author.objects.only('pk'))

result:

- db: SELECT ... FROM "testapp_author"
- db: SELECT ... FROM "testapp_author"

It will be helpfull to not hide selected columns, because without reading the code in parallel we don't know how many fields are concerned by the query.

I will propose a PR.