dev-guide/cluster-version-operator/OWNERS: Add Petr
Now that he's on the updates team.  And keep Scott around, since he
looks over update-y docs.  Otherwise, prune some emeritus members to
align with the CVO repository's current approvers [1].
[1]:
# See the OWNERS docs: https://git.k8s.io/community/contributors/guide/owners.md
approvers:
- - smarterclayton
- - abhinavdahiya
- sdodson
- wking
- - vrutkovs
- jottofar
- LalatenduMohanty
+ - petr-muller
