Update minimum version of docker compose supported

Created by: caugustus-sourcegraph

Update the minimum version requirements for docker-compose to 1.29.0. This version was released 2021-04 and enables us to use the service_completed_successfully dependency condition to improve reliability of deployments.

If customers cannot upgrade their versions, they can remove any service_completed_successfully dependencies in their docker-compose file, but will experience a degraded experience. We don't want to recommend this approach so I'm not documenting it officially.

Closes https://github.com/sourcegraph/sourcegraph/issues/32077.

Test plan

N/A, trivial doc change