Change our AWS_RETRY_MODE to standard

[poodlewars]

We use the SDK at the moment, legacy.

The recommended one is standard. We can set this in code when we create the S3 client.

This ticket should include some testing on Man Group infra to compare the performance characteristics and success rates of ListObjects call with the new retry mode.

https://docs.aws.amazon.com/sdkref/latest/guide/feature-retry-behavior.html#standardvsadaptive