Update free user limit alert copy for non-owner roles

What does this MR do and why?

This MR implements https://gitlab.com/gitlab-org/gitlab/-/issues/393785 which updates the copy on the alert that is displayed for non-owners when their namespace is over the free user limit.

Copy Updates

• Header: Your top-level group [group name] will move to a read-only state soon
• Body: The top-level group, including any subgroups and projects, will be placed into a read-only state soon. To retain write access, ask your top-level group Owner to reduce the number of users to 5 or less. An Owner of the top-level group can also start a free trial or upgrade to a paid tier, which do not have user limits. The Owners of the top-level group have also been notified.

Expected behavior

1. Current pre-existing criteria for alerts display remains the same (free, private, top-level namespace with 6+ users should see the alerts)
2. User should not be able to dismiss the alerts

Screenshots or screen recordings

Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

• Setup gdk to simulate SaaS - https://docs.gitlab.com/ee/development/ee_features.html#simulate-a-saas-instance and restart GDK

bin/rails c

ApplicationSetting.first.update(dashboard_limit_enabled: false)
Feature.disable(:free_user_cap)
Feature.disable(:free_user_cap_new_namespaces)
Feature.disable(:preview_free_user_cap)

• Sign in as free user. Create private group and private project inside.
• Add 4 members.

bin/rails c

ApplicationSetting.first.update(dashboard_limit_enabled: true, dashboard_notification_limit: 3, dashboard_limit: 5, dashboard_enforcement_limit: 5)
Feature.enable(:preview_free_user_cap)

• Sign out. Sign in as another group member that is not an owner.
• Go to the group info page. Check alert is present, with updated copy.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #393785