Fix acceptance tests

Author: stevebux

tests/constants/api-constants.ts

@@ -2,7 +2,7 @@ export const SUPPLIER_LETTERS = "letters";
 export const SUPPLIER_API_URL_SANDBOX =
   "https://internal-dev-sandbox.api.service.nhs.uk/nhs-notify-supplier";
 export const AWS_REGION = "eu-west-2";
-export const envName = process.env.PR_NUMBER ?? "main";
+export const envName = process.env.TARGET_ENVIRONMENT;
 export const API_NAME = `nhs-${envName}-supapi`;
 export const LETTERSTABLENAME = `nhs-${envName}-supapi-letters`;
 export const SUPPLIERID = "TestSupplier1";