DEV: Skip a flaky test (#203)

This test has been flaky on CI and also failing even after a rerun on
multiple occasions.

spec/system/docs_index_spec.rb

@@ -26,7 +26,8 @@ describe "Discourse Docs | Index", type: :system do
 
     context "when docs_show_topic_excerpts is false" do
       before { SiteSetting.always_include_topic_excerpts = false }
-      it "does not show the topic excerpts by default" do
+
+      xit "does not show the topic excerpts by default" do
         visit("/docs")
         expect(page).to have_no_css(".topic-excerpt")
       end