HierarchicalCohort: Remove unused status field

[tenzen-y]

What type of PR is this?

/kind cleanup

What this PR does / why we need it:

The cohortStatus field is always empty. To avoid confusing, removing unneeded field would be better. Similar reason: https://github.com/kubernetes-sigs/kueue/pull/3305

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?

NONE

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[mimowo]

/lgtm /approve Let's re-add it when needed. cc @gabesaba

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 79a89b1c7aa1192b846bc69df8279a556cd21757

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: mimowo, tenzen-y

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