bump UpdatePolicy MaxBatchSize 1 -> 5
bump UpdatePolicy MaxBatchSize 1 -> 5

One instance at a time takes a very long time to cycle through 60-80
instances.

caremonkey/buildkite-aws-elastic-stack,caremonkey/buildkite-aws-elastic-stack,holmesjr/elastic-ci-stack-for-aws,buildkite/elastic-ci-stack-for-aws,holmesjr/elastic-ci-stack-for-aws