test: increase test duration

Increase the duration of the test to make sure that at least one
intermediate report is produced before the workers are terminated
due to OOM. An assertion in an e2e test relies on having at least
one intermediate report produced:

https://github.com/artilleryio/artillery/blob/5a01e3632c4b6959ad94299bd7caf37397331c6b/packages/artillery/test/cloud-e2e/fargate/memory.test.js#L22

packages/artillery/test/cloud-e2e/fargate/fixtures/memory-hog/memory-hog.yml

@@ -7,7 +7,7 @@ config:
   target: http://asciiart.artillery.io:8080
   phases:
     - arrivalRate: 1
-      duration: 10
+      duration: 12
   processor: './processor.js'
 
 scenarios: