DEV: Unskip system tests and avoid predicate matchers (#224)

RSpec predicate matchers provide poor output when tests fail.
This commit switches to Capybara RSpec matches so that we get more
debugging information as to why these tests are flaky...

Author: tgxworld

spec/system/admin_update_spec.rb

@@ -4,25 +4,16 @@
 
 RSpec.describe "Admin update", type: :system do
   fab!(:admin)
-  let(:au_page) { PageObjects::Pages::AdminUpdate.new }
+  let(:admin_update_page) { PageObjects::Pages::AdminUpdate.new }
 
-  before do
-    sign_in(admin)
-    au_page.visit
-  end
-
-  # flaky test /t/133037
-  xit "shows the update page" do
-    expect(au_page).to be_displayed
-  end
+  before { sign_in(admin) }
 
-  # flaky test /t/133033
-  xit "shows the core repo" do
-    expect(au_page).to have_repo(name: "Discourse")
-  end
+  it "displays the admin update page with the right respositories" do
+    visit("/admin/update")
 
-  # flaky test /t/133032
-  xit "shows the docker_manager plugin repo" do
-    expect(au_page).to have_repo(name: "Docker Manager", url: "https://meta.discourse.org/t/12655")
+    expect(page).to have_css("h3", exact_text: I18n.t("js.admin.docker.update_title"))
+    expect(page).to have_css("tr.repo .repo__name", exact_text: "Discourse")
+    expect(page).to have_css("tr.repo .repo__name", exact_text: "Docker Manager")
+    expect(page).to have_css("tr.repo .repo__about a[href='https://meta.discourse.org/t/12655']")
   end
 end