Update Supplementary Billing flag route (#2608)

DEFRA/water-abstraction-system#1239

During recent refactoring for the Supplementary billing flag process, the route was updated to better reflect the naming conventions in the repo. This PR is to update the routes when the service is called.

src/lib/connectors/system/supplementary-billing.js

@@ -8,7 +8,7 @@ const { serviceRequest } = require('@envage/water-abstraction-helpers')
  * @return {Promise}
  */
 const flagSupplementaryBilling = (chargeVersionId) => {
-  const url = `${config.services.system}/licences/supplementary-flag`
+  const url = `${config.services.system}/licences/supplementary`
   const options = {
     body: {
       chargeVersionId