Fix syntax error in release.yaml

[imjasonh]

This caused some failure emails, e.g., https://github.com/imjasonh/kaniko/actions/runs/1373017777

Submitter Checklist

These are the criteria that every PR should meet, please check them off as you
review them:

• [n/a] Includes unit tests
• [n/a] Adds integration tests if needed.

See the contribution guide for more details.

Reviewer Notes

• The code flow looks good.
• Unit tests and or integration tests added.

Release Notes

none

[imjasonh]

Friendly ping, I think this blocks any future releases using this workflow config.

I'm not sure why integration tests are failing. It looks like a flake, I've retried it to be sure.

[imjasonh]

Ping, this is still broken at head. You won't be able to cut a release, and contributors will get spammed with spurious failures until this is fixed.

[priyawadhwa]

Seems like the failing test is a flake unrelated to this PR, I'm going to go ahead and merge this so people stop getting pinged
!