Refresh cluster-api-openstack-maintainers

[mandre]

Removed trown and flaper87.
Added Fedosin and mandre.

What this PR does / why we need it:

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
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Special notes for your reviewer:

1. Please confirm that if this PR changes any image versions, then that's the sole change this PR makes.

Release note:

[openshift-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: mandre
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• chaosaffe
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• chrigl
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• dims
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• m1093782566
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