Remove verify=False as default

[okurz]

Ignoring certificate errors is actually not a nice default. Maybe this is still there from when I started and I forgot to change that and nobody else cared. However, it would be great if one had to specify e.g. --insecure explicitly (even if that means we'll have to do that in our pipelines). Of course you can keep this for the sake of this PR as it has nothing to do with your changes.

Originally posted by @Martchus in #434 (comment)