Restrict issues settings page access to maintainers+ only

Problem

The issues settings page at the root group level, where configurable statuses and the custom fields management section are available, should only be accessible to users with a maintainer or higher role.

Currently, if a user without maintainer+ access navigates directly to the URL (e.g., https://gitlab.com/groups/gitlab-com/-/settings/issues), they can still view the page.

Proposed Solution

Restrict issues settings page access to maintainers+ only.