IMPORT, schema changes don't use protected ts

[rmloveland]

Fixes DOC-5193

Relates to cockroachdb/cockroach#68043

[github-actions]

Files changed:

• v21.2/architecture/storage-layer.md
• v22.1/architecture/storage-layer.md
• v22.2/architecture/storage-layer.md
• v23.1/architecture/storage-layer.md

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[rmloveland]

Hi @adityamaru do you mind taking a look at this docs change re: IMPORT and protected timestamps?

[adityamaru]

Thanks!

[stevendanna]

I believe some parts of schema changes in 23.1 do technically use protected timestamps.

[adityamaru]

🤦 I found all usages of Protect when reviewing this but I forgot that they switched over to using a different jobs PTS manager. Apologies @rmloveland I believe backfill schema changes still use PTS records.

[rmloveland]

Thanks @stevendanna and @adityamaru for pointing this out!

I have filed DOC-7465 to update this to add back schema changes to the list of things that use protected ts

@stevendanna do you think simply adding the link back to the list (that was removed in this PR) would suffice?