Fix test-related issues (#17888)

* Remove obsolete RSS::Serializer test

Since #17828, RSS::Serializer no longer has specific code for deleted statuses,
but it is never called on deleted statuses anyway.

* Rename erroneously-named test files

* Fix failing test

* Fix test deprecation warnings

* Update CircleCI Ruby orb

1.4.0 has a bug that does not match all the test files due to incorrect
globbing

spec/controllers/settings/exports/bookmarks_controller_spec.rb

@@ -3,11 +3,16 @@ require 'rails_helper'
 describe Settings::Exports::BookmarksController do
   render_views
 
-  describe 'GET #index' do
-    it 'returns a csv of the bookmarked toots' do
-      user = Fabricate(:user)
-      user.account.bookmarks.create!(status: Fabricate(:status, uri: 'https://foo.bar/statuses/1312'))
+  let(:user)    { Fabricate(:user) }
+  let(:account) { Fabricate(:account, domain: 'foo.bar') }
+  let(:status)  { Fabricate(:status, account: account, uri: 'https://foo.bar/statuses/1312') }
 
+  describe 'GET #index' do
+    before do
+      user.account.bookmarks.create!(status: status)
+    end
+
+    it 'returns a csv of the bookmarked toots' do
       sign_in user, scope: :user
       get :index, format: :csv