chore(rel): remove legacy scripts and update utils (#1125)

This PR removes some outdated an unmaintained scripts that were provided
to assist customers in setting up Sourcegraph via Docker Compose in
different environments.

From what we have seen, very few customers use these scripts. In
addition, users looking to install Docker Compose are likely best served
by following the official [Docker Compose
documentation](https://docs.docker.com/compose/install/), rather than
using potentially outdated scripts.

### Checklist

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* [NA] Sister
[deploy-sourcegraph](https://github.com/sourcegraph/deploy-sourcegraph)
change:
* [NA] Sister
[customer-replica](https://github.com/sourcegraph/deploy-sourcegraph-docker-customer-replica-1)
change (if necessary, for any changes affecting pure-docker or
configuration):
* [NA] All images have a valid tag and SHA256 sum
### Test plan

CI test pipeline

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