Simplify notification check for participating

app/models/notification_recipient.rb

@@ -50,7 +50,7 @@ class NotificationRecipient
     when :mention
       @type == :mention
     when :participating
-      !excluded_participating_action? && %i[participating mention watch].include?(@type)
+      @custom_action == :failed_pipeline || %i[participating mention].include?(@type)
     when :custom
       custom_enabled? || %i[participating mention].include?(@type)
     when :watch
@@ -106,12 +106,6 @@ class NotificationRecipient
     NotificationSetting::EXCLUDED_WATCHER_EVENTS.include?(@custom_action)
   end
 
-  def excluded_participating_action?
-    return false unless @custom_action
-
-    NotificationSetting::EXCLUDED_PARTICIPATING_EVENTS.include?(@custom_action)
-  end
-
   private
 
   def read_ability

app/models/notification_setting.rb

@@ -54,14 +54,11 @@ class NotificationSetting < ApplicationRecord
     self.class.email_events(source)
   end
 
-  EXCLUDED_PARTICIPATING_EVENTS = [
-    :success_pipeline
-  ].freeze
-
   EXCLUDED_WATCHER_EVENTS = [
     :push_to_merge_request,
-    :issue_due
-  ].push(*EXCLUDED_PARTICIPATING_EVENTS).freeze
+    :issue_due,
+    :success_pipeline
+  ].freeze
 
   def self.find_or_create_for(source)
     setting = find_or_initialize_by(source: source)