relabel "guides" to "Best practices" and move under "Using Notify" primary nav

[dmvancura]

with new "Using Notify" content going live (likely) by 1/9/25 we can keep the Best practices content as it was in tests, but relabel it as such i.e., get rid of the "Guides" section label.

and "Best practices" section/label is moved under the "Using Notify" content section

may require, or may already have, the site nav and side nav outlined in wireframe