When restoring a backup, disable emails.

This prevents accidental sending of emails after a restore before
the admin has had a chance to review everything.

app/controllers/admin/backups_controller.rb

@@ -77,6 +77,7 @@ class Admin::BackupsController < Admin::AdminController
       client_id: params.fetch(:client_id),
       publish_to_message_bus: true,
     }
+    SiteSetting.set_and_log(:disable_emails, true, current_user)
     BackupRestore.restore!(current_user.id, opts)
   rescue BackupRestore::OperationRunningError
     render json: failed_json.merge(message: I18n.t("backup.operation_already_running"))