FIX: Do not return muted child categories termless hashtag search (#19526)

We generally do not return muted child categories to the user
if they have muted the parent category, this commit respects that
rule for CategoryHashtagDataSource

spec/services/category_hashtag_data_source_spec.rb

@@ -91,6 +91,15 @@ RSpec.describe CategoryHashtagDataSource do
       )
       expect(described_class.search_without_term(guardian, 5).map(&:slug)).not_to include("random")
     end
+
+    it "does not return child categories where the user has muted the parent" do
+      CategoryUser.create!(
+        user: user,
+        category: parent_category,
+        notification_level: CategoryUser.notification_levels[:muted],
+      )
+      expect(described_class.search_without_term(guardian, 5).map(&:slug)).not_to include("random")
+    end
   end
 
   describe "#search_sort" do