Mention the requirement of operator-backup image 1.3.5 if "defaultRecoveryMethod" is set to anything other than "none"

Due to K8S-2423 there is a requirement of operator-backup image version 1.3.5 if "defaultRecoveryMethod" is anything other than "none".

I don't see it mentioned here or in the release notes for CAO 2.5.0:

https://docs.couchbase.com/operator/2.5/resource/couchbasebackup.html#couchbasebackups-spec-defaultrecoverymethod