Fix update_attribute function parameters syntax

Inherited function "update_attribute", while in the
project->jira_service context, has signature: (:attribute, value) and
not (attribute: value).

doc/administration/troubleshooting/gitlab_rails_cheat_sheet.md

@@ -288,7 +288,7 @@ To change all Jira project to use the instance-level integration settings:
    ```ruby
    jira_service_instance_id = JiraService.find_by(instance: true).id
    JiraService.where(active: true, instance: false, template: false, inherit_from_id: nil).find_each do |service|
-     service.update_attribute(inherit_from_id: jira_service_instance_id)
+     service.update_attribute(:inherit_from_id, jira_service_instance_id)
    end
    ```