Rewording needed on Storage Settings page

This regards the following page:

https://docs-staging.couchbase.com/server/7.1/learn/buckets-memory-and-storage/storage-settings.html

A bunch of changes are needed. The page reads quite odd at the moment.

1. Remove the page heading line. It is not needed and not very correct.

Couchbase Server provides persistence, whereby certain items are stored on disk as well as in memory; and reliability is thereby enhanced.

2. Remove the whole 'Understanding Couchbase Storage' section. It does not belong here and seems like a repetition of information covered elsewhere.