Use a list of links for admin stats events

Using <h3> headings for the links had two disadvantages.

First, it was the wrong heading level to use, since there was no <h2>
tag before it.

Second, headings are supposed to be followed by content associated to
that heading; here, we had no content following the headings.

So we're using a list of links and giving it a heading. We're adding
styles so the page still looks like it used to, although these styles
are certainly asking for improvements.

spec/components/admin/stats/event_links_component_spec.rb

@@ -0,0 +1,17 @@
+require "rails_helper"
+
+describe Admin::Stats::EventLinksComponent do
+  it "renders an <h2> heading followed by a list of links" do
+    render_inline Admin::Stats::EventLinksComponent.new(
+      %w[legislation_annotation_created legislation_answer_created]
+    )
+
+    expect(page).to have_css "h2", exact_text: "Graphs"
+    expect(page).to have_link count: 2
+
+    page.find("ul") do |list|
+      expect(list).to have_link "legislation_annotation_created"
+      expect(list).to have_link "legislation_answer_created"
+    end
+  end
+end