hugo: use new hugo-book edit link feature

Remove custom footer template, this helps to reduce future
incompatibility by minimizing overwritten templates.

Author: anthraxx

config.toml

@@ -29,3 +29,5 @@ theme = "hugo-book"
 
 [params]
   BookSearch = false
+  BookRepo = 'https://github.com/uapi-group/uapi-group.github.io'
+  BookEditLink = '{{ .Site.Params.BookRepo }}/edit/main/{{ .Path }}'