Revert back to using gophish/gophish

[dav3r]

💡 Summary

When it is no longer necessary to use our own fork of gophish/gophish, revert the changes from PR #24.

Motivation and context

After the maintainers of gophish/gophish merge our mission-critical PRs (e.g. gophish/gophish#1486), we should no longer need to maintain our own fork of that repo. When that happens, we can revert this repo back to pulling the release binary from gophish/gophish.

Implementation notes

None

Acceptance criteria

How do we know when this work is done?

• The Dockerfile for this repo pulls the release archive from gophish/gophish
• A functional Docker image can be built with this Dockerfile