Update offer-api

[andygout]

next-newsletter-signup's healthchecks are currently failing with:

{
	"id": "all-services-registered-us",
	"name": "Metrics: All services for newsletter-signup registered in next-metrics in us",
	"ok": false,
	"checkOutput": "https://api.ft.com/membership/offers/v2/ce949b25-9ff1-3e92-e136-b7858bb55214, https://api.ft.com/membership/offers/v2/a8854b82-d47f-e1f1-83f2-e236b6339eaa services called but no metrics set up.",
	"lastUpdated": "2024-06-07T13:37:57.516Z",
	"panicGuide": "See next-metrics/lib/metrics/services.js and set metrics for the service, then release next-metrics and rebuild this app.",
	"severity": 3,
	"businessImpact": "We don't have any visibility with unregistered services.",
	"technicalSummary": "Set up services' metrics in next-metrics/lib/metrics/services.js to send to Graphite."
},

This is as a result of these recent changes to that app (https://github.com/Financial-Times/next-newsletter-signup/pull/813), which fetches offer data from the Offer API with which to populate the prices for the niche newsletter paid subscriptions.

Inside Politics production environment offer ID

https://api.ft.com/membership/offers/v2/ce949b25-9ff1-3e92-e136-b7858bb55214

---

Unhedged production environment offer ID

https://api.ft.com/membership/offers/v2/a8854b82-d47f-e1f1-83f2-e236b6339eaa

---

N.B.

I have confirmed that the existing values that this PR removes are deprecated — see this Slack thread.

---

Ticket

• ACQ-2811: Next Newsletter Signup - Metrics: All services for newsletter-signup registered in next-metrics in us