Provide output when running migrations

[michaelkuhn]

When upgrading my installation, I noticed that miniflux -migrate does not provide any output by default. This can be a bit confusing since one cannot be sure whether anything has happened. Use Info instead of Debug to provide some basic output by default.

Do you follow the guidelines?

• [x] I have tested my changes
• [x] There is no breaking changes
• [x] I really tested my changes and there is no regression
• [ ] Ideally, my commit messages follow the Conventional Commits specification
• [x] I read this document: https://miniflux.app/faq.html#pull-request