controllers: fix index redirect param to not redirect to .html extension.

Fix searches like this:

* https://danbooru.donmai.u/wiki_pages?search[title]=touhou&redirect=true

To redirect to this:

* https://danbooru.donmai.u/wiki_pages/touhou

Instead of this:

* https://danbooru.donmai.u/wiki_pages/touhou.html

This also fixes redirects when searching for users on profile pages, and during pagination on media
asset show pages.

app/controllers/application_controller.rb

@@ -75,7 +75,11 @@ class ApplicationController < ActionController::Base
   end
 
   def redirect_to_show(items)
-    redirect_to send("#{controller_path.singularize}_path", items.first, format: request.format.symbol)
+    if request.format.html?
+      redirect_to send("#{controller_path.singularize}_path", items.first)
+    else
+      redirect_to send("#{controller_path.singularize}_path", items.first, format: request.format.symbol)
+    end
   end
 
   def is_redirect?(items)