Docs: [AEA-6528] - Update the OAS file to say the PSU is in Beta (#2968)

## Summary

- Routine Change

### Details

Marks the PSU as "in beta" in the OAS spec.

Author: wildjames

packages/specification/eps-custom-prescription-status-update-api.yaml

@@ -12,15 +12,15 @@ info:
     email: api.management@nhs.net
   description: |
     ## Overview
-    The Custom Prescription Status Update API is restricted to dispensing suppliers with an existing prescription 
-    status update solution, who can onboard to provide updates to patients on a national scale via the NHS App 
+    The Custom Prescription Status Update API is restricted to dispensing suppliers with an existing prescription
+    status update solution, who can onboard to provide updates to patients on a national scale via the NHS App
     (and other third parties in the future) by September 2024.
 
     You can:
     * enable patients to know when their prescription is ready
     * enable dispensing suppliers to push status information about electronic prescriptions
     ## Who can use this API
-    The Custom Prescription Status Update API is intended for those dispensing suppliers who have signed the MOU to 
+    The Custom Prescription Status Update API is intended for those dispensing suppliers who have signed the MOU to
     supply status updates by September 2024, so they can provide and push the information required to a central NHS data store.
     ## Related APIs
     The following APIs are related to the "Custom Prescription Status Update" API:

packages/specification/eps-prescription-status-update-api.yaml

@@ -27,7 +27,7 @@ info:
     * [Electronic Prescriptions Service Dispensing](https://digital.nhs.uk/developer/api-catalogue/eps-fhir-dispensing-api): the national service for dispensing prescriptions across health and social care.
     * [Prescriptions for Patients](https://digital.nhs.uk/developer/api-catalogue/prescriptions-for-patients-fhir-api-v2): the national service to retrieve prescriptions data for individual patients from the Electronic Prescription Service (EPS), for use in patient-facing applications.
     ## API Status and Roadmap
-    This API is [in development](https://digital.nhs.uk/developer/guides-and-documentation/reference-guide#statuses), meaning the API will soon be available for testing via a sandbox service or an integration environment - but we expect to make breaking changes based on developer feedback.
+    This API is [in beta](https://digital.nhs.uk/developer/guides-and-documentation/reference-guide#statuses), which means it is being used by a small number of suppliers and could still be subject to breaking changes.
     ## Service Level
     This API is a silver service, meaning it is operational and supported between 8am and 6pm, Monday to Friday, but not bank holidays.
     For more details see [service levels](https://digital.nhs.uk/developer/guides-and-documentation/reference-guide#service-levels).