Update Service Account Issuer Migration doc

[elliotdobson]

Update Service Account Issuer Migration documentation to include additionalServiceAccountIssuers migration procedure. Follow up from #16541 now that I have tested the migration using additionalServiceAccountIssuers.

[k8s-ci-robot]

Hi @elliotdobson. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[hakman]

/ok-to-test

[rasta-rocket]

Just one info here, we tried it on our side and it worked perfectly 👍
Thank you @elliotdobson

[elliotdobson]

Hey @hakman, can you approve this please?

[hakman]

Sorry for missing this @elliotdobson, thanks again!
/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: hakman

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [hakman]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[hakman]

/retest