DEV: No longer preload categories (#24950)

Categories will no longer be preloaded when `lazy_load_categories` is
enabled through PreloadStore.

Instead, the list of site categories will continue to be populated
by `Site.updateCategory` as more and more categories are being loaded
from different sources (topic lists, category selectors, etc).

spec/models/site_spec.rb

@@ -183,17 +183,6 @@ RSpec.describe Site do
         DiscoursePluginRegistry.clear_modifiers!
       end
     end
-
-    context "when lazy_load_categories" do
-      before { SiteSetting.lazy_load_categories = true }
-
-      it "limits the number of categories" do
-        stub_const(Site, "LAZY_LOAD_CATEGORIES_LIMIT", 1) do
-          categories = Site.new(Guardian.new).categories
-          expect(categories.size).to eq(1)
-        end
-      end
-    end
   end
 
   it "omits groups user can not see" do