Remove backend workflow write to s3 for activity

[manasaV3]

With the metrics endpoint being completely powered by the dynamo data, we can remove the old activity update workflow in the backend module that writes to s3.
As we remove the activity update workflow in the backend module, we should also remove the associated infrastructure components, as they are no longer needed. This includes the snowflake credentials provided on to the lambda, and event bridge components setup for triggering the workflow.