DEV: Resolve state leak causing flaky test (#205)

spec/system/docs_index_spec.rb

@@ -27,7 +27,7 @@ describe "Discourse Docs | Index", type: :system do
     context "when docs_show_topic_excerpts is false" do
       before { SiteSetting.always_include_topic_excerpts = false }
 
-      xit "does not show the topic excerpts by default" do
+      it "does not show the topic excerpts by default" do
         visit("/docs")
         expect(page).to have_no_css(".topic-excerpt")
       end
@@ -49,6 +49,8 @@ describe "Discourse Docs | Index", type: :system do
         Theme.clear_cache!
       end
 
+      after { Theme.clear_cache! }
+
       it "shows the excerpts" do
         visit("/docs")
         expect(page).to have_css(".topic-excerpt", text: topic_1.excerpt)