🌱 increase wait-worker-nodes in clusterctl upgrade tests

[cahillsf]

What this PR does / why we need it:

will hopefully reduce the flakiness of some clusterctl upgrade tests

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Relates to #11209

/area testing

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[k8s-ci-robot]

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[cahillsf]

/test pull-cluster-api-e2e-main