Update doc/settings/database.md to add a note suggesting an ANALYZE VERBOSE; query for RDS users
Based on the findings of this support incident, it was recommended that GitLab add a call-out in our documentation identifying ANALYZE VERBOSE;
to regenerate postgres query plans following a major-version upgrade.
Given that this does not appear to be the only support case where this advice has proven efficacious; it seems prudent to document this, for the benefit of future customers or support personnel seeking advice on this issue.