[3/N] Use pyupgrade --py39-plus to improve code

[cyyever]

What does this PR do?

Continued work to adopt Python 3.9 syntax. Follows #36857 .

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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• Did you write any new necessary tests?

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[github-actions]

Hi 👋, thank you for opening this pull request! The pull request is converted to draft by default. The CI will be paused while the PR is in draft mode. When it is ready for review, please click the Ready for review button (at the bottom of the PR page). This will assign reviewers.

[Rocketknight1]

Looks good to me, with one comment!

[Rocketknight1]

Sorry about the failing tests - try rerunning / updating until they pass, then ping me to merge it!

[cyyever]

Without TF jobs, hope it becomes green.

[Rocketknight1]

Hi @cyyever, is this redundant with #37039? Should we close this one and use #37039 instead?

[cyyever]

@Rocketknight1 Can

[github-actions]

Hi 👋, thank you for opening this pull request! The pull request is converted to draft by default. The CI will be paused while the PR is in draft mode. When it is ready for review, please click the Ready for review button (at the bottom of the PR page). This will assign reviewers and trigger CI.

[cyyever]

@Rocketknight1 Base on others' opinions, it's better to deal with smaller PRs like this one.

[Rocketknight1]

@cyyever sure! In that case, please try make fixup and/or rebasing/merging to get the tests to pass, as usual, and then ping me when you're ready to merge.

[cyyever]

@Rocketknight1 Unrelated failures. We can wait them become green.