DEV: Move a plugin related system spec to footnote plugin (#31230)

In a previous PR, I introduced this system spec that checks that a sidebar link is auto-generated for certain plugins.

This causes problems, because the core test suite can be run with plugins either enabled or disabled, causing flaky tests.

plugins/footnote/spec/system/admin_sidebar_navigation_spec.rb

@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+RSpec.describe "Admin | Sidebar Navigation", type: :system do
+  fab!(:admin)
+
+  let(:sidebar) { PageObjects::Components::NavigationMenu::Sidebar.new }
+
+  before do
+    SiteSetting.navigation_menu = "sidebar"
+    SiteSetting.admin_sidebar_enabled_groups = [Group::AUTO_GROUPS[:admins]]
+
+    sign_in(admin)
+  end
+
+  it "adds an auto-generated plugin link to the admin sidebar" do
+    SiteSetting.enable_markdown_footnotes = true
+
+    visit("/admin")
+
+    sidebar.toggle_section(:plugins)
+
+    expect(page).to have_css(
+      ".sidebar-section-link-content-text",
+      text: I18n.t("js.footnote.title"),
+    )
+  end
+end

spec/system/admin_sidebar_navigation_spec.rb

@@ -337,19 +337,4 @@ describe "Admin | Sidebar Navigation", type: :system do
       ],
     )
   end
-
-  it "adds auto-generated plugin links for plugins with settings" do
-    skip if Discourse.plugins.empty?
-
-    SiteSetting.enable_markdown_footnotes = true
-
-    visit("/admin")
-
-    sidebar.toggle_section(:plugins)
-
-    expect(page).to have_css(
-      ".sidebar-section-link-content-text",
-      text: I18n.t("js.footnote.title"),
-    )
-  end
 end