kvserver: default kv.rangefeed.catchup_scan_iterator_optimization.enabled to true

[cockroach-teamcity]

Exalate commented:

cockroachdb/cockroach#73473 --- Release note (ops change): The default value of the kv.rangefeed.catchup_scan_iterator_optimization.enabled cluster setting is now true.

Jira Issue: DOC-2157

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