Backport of Updated Nomad Secret Engine docs with proper terminology into release/1.9.x

[hc-github-team-secure-vault-core]

Backport

This PR is auto-generated from #16859 to be assessed for backporting due to the inclusion of the label backport/1.9.x.

WARNING automatic cherry-pick of commits failed. Commits will require human attention.

merge conflict error: POST https://api.github.com/repos/hashicorp/vault/merges: 409 Merge conflict []

The below text is copied from the body of the original PR.

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This PR accomplishes what PR 8983 meant to do.

Since PR 8983 was opened back in 2020, it's troublesome to merge the PR. We'll fix the terminology with this PR and close PR 8983.

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Overview of commits

• 88ab260

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