when placing {{Old XFD Multi}} template on redirected talk pages, remove the redirect instead of appending

[NovemLinguae]

Reported by wbm1058 at https://en.wikipedia.org/wiki/Wikipedia_talk:XFDcloser#Old_afd_templates_placed_on_talk_pages_of_redirects

In this diff, the redirect AND redirect category shell should be deleted before adding the template. In other words, we should be overwriting the entire page if it is a redirect, instead of appending a string to the top of it.