Prefer g_info() over g_message()

Libraries shouldn't really use `g_message()` as it will show up in
consumer application outputs. Let's use `g_info()` instead.

Fixes #40
6 jobs for wip/nielsdg/no-g-message in 7 minutes and 37 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #626217
fedora:asan

00:07:01

passed #626219
fedora:coverage

00:05:37

69.8%
passed #626218
fedora:ubsan

00:07:12

passed #626216
fedora:Werror

00:06:35

 
  Deploy
passed #626220
pages

00:00:23

passed pages:deploy

00:00:01