test(download): licence the estate this spec needs

The estate ships no licence key, so it runs on the free tier, and the free tier
disables file upload - which is exactly what the audit case needs. Whether it
could run depended on another spec having planted a key earlier in the run: the
key persists in the estate config, so the case passed or failed on spec order.

loginAndUpdateValidKey(true) plants one here. csv-limited, which asserts the
free-tier modal, runs first in cypress-specs.sh and is unaffected; download runs
last, so nothing downstream inherits the key.

Found by running the spec against the mock estate locally: the upload input
never rendered, the modal read "Locked Feature (File Upload) ... site id (123)",
and the run went 7/7 green once the key was planted.

client/cypress/e2e/download.cy.ts

@@ -15,7 +15,13 @@ import { deleteDownloadsFolder } from '../util/deleteDownloadFolder'
 context('download files test: ', function () {
   this.beforeAll(() => {
     cy.visit(`${hostUrl}/SASLogon/logout`)
-    cy.loginAndUpdateValidKey()
+    /* the estate ships no licence, so it runs on the free tier - and the free
+      tier disables file upload, which is the whole point of the audit case.
+      Asking for a licensed estate here means the spec does not depend on
+      another spec having planted a key first: the key persists in the estate's
+      config, so whether this case could run depended on the order the specs
+      were sharded into. */
+    cy.loginAndUpdateValidKey(true)
   })
 
   this.beforeEach(() => {