Fix(Subscription errors): handle expired + connectivity error

What does this MR do and why?

This MR updates the errors messages for the subscription activation:

• Handle expired license error: https://gitlab.com/gitlab-org/gitlab/-/issues/355794
• Update wording for connectivity error: https://gitlab.com/gitlab-org/gitlab/-/issues/355790

Screenshots or screen recordings

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Situation	Before	After
License expired
Connectivity issue

How to set up and validate locally

1. Apply this patch: simulate-connectivity-error.patch

2. Visit the subscription page: http://localhost:3000/admin/subscription

3. Click the Enter activation code button and type in a valid activation code (purchased through CustomersDot)

4. See the (updated) connectivity error message appear

5. Apply this patch: simulate-license-expired-error.patch

6. Visit the subscription page: http://localhost:3000/admin/subscription

7. Click the Enter activation code button and type in a valid activation code (purchased through CustomersDot)

8. See the expired license error message appear

MR acceptance checklist

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