Remove repo module attribute from version_queries

[FlorianGerhardt]

This PR removes the @repo module attribute from VersionQueries.
I had the problem

** (UndefinedFunctionError) function Repo.all/1 is undefined (module Repo is not available)

when I used distillery to create a release.
Compared to other libraries, the usage of module attributes seems to be the difference so I tried to replace them and it worked.
I am still pretty new to Elixir and not sure what exactly the problem was, but my guess is that Distillery compiles every file beforehand and according to this: https://elixir-lang.org/getting-started/module-attributes.html#as-constants

Every time an attribute is read inside a function, a snapshot of its current value is taken. In other words, the value is read at compilation time and not at runtime.
it looked like the Repo module was not defined at compilation time.

[izelnakri]

Thanks for the fix @FlorianGerhardt ! I will very likely merge this PR, will do a more in-depth check in few days. Meanwhile feel free to add yourself to credits ;)