Convert tags controller spec to system and request specs (#31708)

spec/system/tags_spec.rb

@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe 'Tags' do
+  describe 'Viewing a tag' do
+    let(:tag) { Fabricate(:tag, name: 'test') }
+
+    it 'visits the tag page and renders the web app' do
+      visit tag_path(tag)
+
+      expect(page)
+        .to have_css('noscript', text: /Mastodon/)
+    end
+  end
+end