Replaces the following blocks/variables with the
`footer` block filled by the `notify_footer`
macro:
- footer_top
- footer_support_links
Our current footer has a few differences
with the GOVUK Frontend one:
1. the columns of links and the meta links have no
headings, visible or structural
2. the line of text saying GDS built this prefixes
the meta links whereas theirs sits on a new
link, after them