Clarify Last Activity as Last GitLab Activity on Usage Quotas page

What does this MR do and why?

Clarify Last Activity as Last GitLab Activity on Seats and Code Suggestions tab on Usage Quotas page.

Related to https://gitlab.com/gitlab-org/customers-gitlab-com/-/issues/7834+

Screenshots or screen recordings

Scenario	Before	After
Seats tab
Exported member list
Code Suggestions tab

How to set up and validate locally

Application setup

1. Customers Dot needs to be setup in order to view the billing page for a group
2. Start GDK in SaaS mode GITLAB_SIMULATE_SAAS=1 gdk start

Group setup

1. Create a Group
2. Buy a Premium or Ultimate Subscription for your group from Settings > Billing

Feature flag

Run the following in your rails console

Feature.enable(:hamilton_seat_management, Namespace.find(your-group-id)

Add-on purchase

Run the following in your rails console

1. Find the namespace

namespace = Namespace.find(your-group-id)

1. Create an Addon

add_on = GitlabSubscriptions::AddOn.find_or_create_by!(name: "code_suggestions") {|e| e.description = "Test"}

1. Create an add-on purchase

GitlabSubscriptions::AddOnPurchase.create!(add_on: add_on, namespace: namespace, expires_on: 1.month.from_now, quantity: 20, purchase_xid: 'A-S0001')

Seats tab

1. Go to Settings > Usage Quotas > Seats tab

Code Suggestions tab

1. Go to Settings > Usage Quotas > Code Suggestions tab

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.