Couple of changes for Magma storage page

Need to change a couple of things on the following page:

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

In the section https://docs-staging.couchbase.com/server/7.1/learn/buckets-memory-and-storage/storage-engines.html#couchstore-and-magma-at-a-glance

1. Replace 'Minimum bucket size' with 'Minimum bucket memory quota'
2. Add another row to the table. Label is 'Minimum memory to data ratio'. Value for Couchstore is 10%. Value for Magma is 1%. This should be the second row in the table after 'minimum bucket memory quota'