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/services/mute_service_spec.rb

@@ -1,9 +1,7 @@
 require 'rails_helper'
 
 RSpec.describe MuteService, type: :service do
-  subject do
-    -> { described_class.new.call(account, target_account) }
-  end
+  subject { described_class.new.call(account, target_account) }
 
   let(:account) { Fabricate(:account) }
   let(:target_account) { Fabricate(:account) }
@@ -21,45 +19,41 @@ RSpec.describe MuteService, type: :service do
       FeedManager.instance.push_to_home(account, status)
       FeedManager.instance.push_to_home(account, other_account_status)
 
-      is_expected.to change {
+      expect { subject }.to change {
         Redis.current.zrange(home_timeline_key, 0, -1)
       }.from([status.id.to_s, other_account_status.id.to_s]).to([other_account_status.id.to_s])
     end
   end
 
   it 'mutes account' do
-    is_expected.to change {
+    expect { subject }.to change {
       account.muting?(target_account)
     }.from(false).to(true)
   end
 
   context 'without specifying a notifications parameter' do
     it 'mutes notifications from the account' do
-      is_expected.to change {
+      expect { subject }.to change {
         account.muting_notifications?(target_account)
       }.from(false).to(true)
     end
   end
 
   context 'with a true notifications parameter' do
-    subject do
-      -> { described_class.new.call(account, target_account, notifications: true) }
-    end
+    subject { described_class.new.call(account, target_account, notifications: true) }
 
     it 'mutes notifications from the account' do
-      is_expected.to change {
+      expect { subject }.to change {
         account.muting_notifications?(target_account)
       }.from(false).to(true)
     end
   end
 
   context 'with a false notifications parameter' do
-    subject do
-      -> { described_class.new.call(account, target_account, notifications: false) }
-    end
+    subject { described_class.new.call(account, target_account, notifications: false) }
 
     it 'does not mute notifications from the account' do
-      is_expected.to_not change {
+      expect { subject }.to_not change {
         account.muting_notifications?(target_account)
       }.from(false)
     end