Fix "Confidential comments" button not saving in project hooks

Closes #50440

app/models/concerns/triggerable_hooks.rb

@@ -6,6 +6,7 @@ module TriggerableHooks
     push_hooks:               :push_events,
     tag_push_hooks:           :tag_push_events,
     issue_hooks:              :issues_events,
+    confidential_note_hooks:  :confidential_note_events,
     confidential_issue_hooks: :confidential_issues_events,
     note_hooks:               :note_events,
     merge_request_hooks:      :merge_requests_events,

changelogs/unreleased/sh-fix-confidential-note-option.yml

+---
+title: Fix "Confidential comments" button not saving in project hooks
+merge_request: 21289
+author:
+type: fixed

spec/controllers/projects/hooks_controller_spec.rb

@@ -30,6 +30,7 @@ describe Projects::HooksController do
         tag_push_events: true,
         merge_requests_events: true,
         issues_events: true,
+        confidential_note_events: true,
         confidential_issues_events: true,
         note_events: true,
         job_events: true,