Remove artifacthub-repo.yml from Chart bundle

Closes #18

This needs to be published to the OCI registry through
oras rather than include it with the release bundle.

https://artifacthub.io/docs/topics/repositories/helm-charts/

Make get-latest-tag retrieve non-suffix tags by default (#16)

Closes #14

Because version comparison in get-latest-tag always prioritizes suffixed
tags (e.g., -alpine) over the ones without, this caused -alpine to be
used as the default appVersion during build.

Remove mention of Varnish Enterprise components

Controller and varnish-discover/varnish-broadcaster support are not present
in the open-source version, so no need to mention them here.