Remove unused name from Auth session documentation

[Greenheart]

Quick fix to make the code sample in the guide work as expected.

The auth guide now consistently uses id instead of mentioning id but actually using name like it did in a previous commit https://github.com/keystonejs/keystone/blob/d0713111f1cdb76d553eb0d65a597620e0d3e056/docs/pages/docs/guides/auth-and-access-control.mdx#add-a-sessiondata-query

This is such a small change so I thought no changeset was needed, but let me know if that's required, and I'll update the PR.

[changeset-bot]

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Latest commit: 5adcda2

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Name	Status	Preview	Updated
keystone-next-docs	✅ Ready (Inspect)	Visit Preview	May 31, 2022 at 2:42AM (UTC)

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