Remove activated feature for removing inactive delegations from stakes cache (backport #21732)

[mergify]

This is an automatic backport of pull request #21732 done by Mergify.
Cherry-pick of c92c09a has failed:

On branch mergify/bp/v1.9/pr-21732
Your branch is up to date with 'origin/v1.9'.

You are currently cherry-picking commit c92c09a8b.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   runtime/src/bank.rs

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   runtime/src/stakes.rs

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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[mergify]

automerge label removed due to a CI failure

[mergify]

automerge label removed due to a CI failure

[jstarry]

Mixed up the backport with another feature removal. Also, this isn't critical