Suggest --no-network on apk del

- [ ] This is a bug report
- [x] This is a feature request
- [x] I searched existing issues before opening this one

### Suggestion

Suggest to add ``--no-network`` to ``apk del`` to use local cache and not ask the network.

See https://github.com/docker-library/dockerfile-validator/blob/master/dockerfile-validator#L160

Start with the referenced dockerfile-validator entry at line 160, then search hadolint for the apk del rule and its tests. Done means the linter suggests --no-network for applicable apk del commands and the relevant checks pass.

Written by the indexing model from the issue text.