Documentation changes for SM rollout

Problem

Add all the documentation changes that will be need as a result of the subscription card new UI changes for SM.

Checklist

Sr. No	Page link	Reference to update	Related issue / MR	Comments	Updated?
1	https://docs.gitlab.com/ee/subscriptions/self_managed/#renew-subscription-manually	Grayed out button for renewal	gitlab!131296 (diffs)		✅
2	https://docs.gitlab.com/ee/subscriptions/self_managed/#enable-or-disable-automatic-subscription-renewal	Enabling/disabling auto-renewal (no more buttons)	gitlab!131296 (diffs)		✅
3	https://docs.gitlab.com/ee/subscriptions/self_managed/#add-seats-to-a-subscription	Adding seats	gitlab!131296 (diffs)		✅
5	https://docs.gitlab.com/ee/subscriptions/self_managed/#upgrade-your-subscription-tier	Upgrade	gitlab!131296 (diffs)		✅

Proposal

Result

The documentation should be updated with the changes made in the new subscription card UI for SM.

Next steps (if any)

How will we measure success?