Increased timeout for the import job test

refs 9fe1274fbe

- Temporary fix to let the CI pass the test. Needs investigation into why MySQL is so much slower comparing to SQLite

ghost/core/test/regression/api/admin/members-importer.test.js

@@ -343,7 +343,7 @@ describe('Members Importer API', function () {
         should.exist(jsonResponse.meta);
 
         // Wait for the job to finish
-        await sleep(10000);
+        await sleep(15000);
 
         assert(!!settingsCache.get('email_verification_required'), 'Email verification should now be required');