Remove /meta_searches/tags page.

This was a search page that let you search for tags, aliases, and
implications at the same time. It never got much use and it's been
broken for a while now (the search form passed the wrong param to the
controller).

test/functional/meta_searches_controller_test.rb

@@ -1,12 +0,0 @@
-require 'test_helper'
-
-class MetaSearchesControllerTest < ActionDispatch::IntegrationTest
-  context "The meta searches controller" do
-    context "tags action" do
-      should "work" do
-        get meta_searches_tags_path, params: {name: "long_hair"}
-        assert_response :success
-      end
-    end
-  end
-end