Dependencies should allow for up to version 4.x.x of puppetlabs-apt

I'm working on another module which requires a newer version of puppetlabs-apt. I also need puppetlabs-postgresql, which is currently pinned to an old version of concat and and apt. The concat dependency got already bumped in the related issue. I created a PR for bumping apt: https://github.com/puppetlabs/puppetlabs-postgresql/pull/869