user-scheduler: update to use kube-scheduler 1.28, from 1.26 - require k8s 1.24+ #2181

Job	Run time
lint_shell_scripts	46s
test (latest, install)	2m 24s
lint_and_validate_templates_with_schema	9s
test (stable, install, --set hub.image.name=quay.io/jupyterhub/k8s-hub-slim --set prePuller.hook....	2m 45s
lint_and_validate_rendered_templates	14s
lint_and_validate_templates_with_schema (v3.5.0)	36s
test (v1.26, install, --set hub.existingSecret=test-hub-existing-secret --set proxy.secretToken=a...	2m 27s
test (v1.26, upgrade, stable, --set proxy.secretToken=aaaa1111 --set hub.cookieSecret=bbbb2222 --...	3m 16s
test (v1.25, upgrade, dev, --set proxy.secretToken=aaaa1111 --set hub.db.type=sqlite-pvc --set si...	3m 17s
test (v1.24, upgrade, 2.0.0, --set proxy.secretToken=aaaa1111 --set hub.cookieSecret=bbbb2222 --s...	3m 40s
	19m 34s

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