gha: use latest action for stale

[andrewhsu]

Following on PR #15935

Unless there is a specific reason to use the older v5 release (feel free to close this PR if so), we should use the latest v9 release.

Backports Required

• none - not a bug fix
• none - this is a backport
• none - issue does not exist in previous branches
• none - papercut/not impactful enough to backport
• v23.3.x
• v23.2.x
• v23.1.x

Release Notes

• none

[rockwotj]

Amazing. I created a template using github, so yeah didn't mean to use the old bot. I wonder if that will fix it's ability to churn through our backlog of stale stuff.

[rockwotj]

Action is now stateful: If the action ends because of operations-per-run then the next run will start from the first unprocessed issue skipping the issues processed during the previous run(s). The state is reset when all the issues are processed. This should be considered for scheduling workflow runs.

Ah yes, that's it. cc: @piyushredpanda

[vbotbuildovich]

ducktape was retried in https://buildkite.com/redpanda/redpanda/builds/43686#018d127c-0f2b-4255-8558-b84e879c1edc