Log mvcc revision compaction as warning

[tedyu]

What type of PR is this?
/kind cleanup

What this PR does / why we need it:
As Fabian stated over #83938, the 'mvcc: required revision has been compacted' message shouldn't be logged as error.
This PR changes the log for this message to warning.

Which issue(s) this PR fixes:
Fixes #

NONE

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

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[fedebongio]

/assign @jpbetz

[mysunshine92]

/lgtm

[jpbetz]

/lgtm

I'm okay with this. I'd expect the log volume to low and proportional to the other log events that will occur if a watch consumer falls outside the compaction window.

[tedyu]

/priority backlog

[wojtek-t]

/approve

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: tedyu, wojtek-t

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