Increase timeout for review-deploy from 15 to 30min

The job genuinely needed more than 15 minutes to do its job,
as it had to clean up more than 20 docs review-apps.

Increasing the timeout will ensure it can do its job properly, even when
a big batch of cleanups come in.

.gitlab/ci/review.gitlab-ci.yml

 review-cleanup:
-  timeout: 15min
+  timeout: 30min
   extends:
     - .default-retry
     - .review:rules:review-cleanup