Cannot delete a remote with multiple fetch refspecs

Steps to reproduce:

>>> import pygit2
>>> repo = pygit2.init_repository(".")
>>> repo.remotes.create("origin", "https://github.com/libgit2/pygit2.git")
>>> repo.remotes.add_fetch("origin", "refs/heads/master:refs/remotes/origin/master")
>>> repo.remotes.add_fetch("origin", "refs/tags/*:refs/tags/*")
>>> repo.remotes.delete("origin")
_pygit2.GitError, entry is not unique due to being a multivar

This is present in the latest release and I also saw it happen (though with different error text) in 0.27

There doesn't appear to be a viable workaround because the libgit2 function for deleting multivars in the config isn't exposed in pygit2. Otherwise I would have tried to remove the multiple fetch entries directly ahead of time and then delete the remote.

Comienza reproduciendo el snippet proporcionado de pygit2 e inspecciona el manejo de la eliminación de remotos y de la configuración expuesto por pygit2. El fix estará completo cuando eliminar un remoto con múltiples refspecs de fetch se realice correctamente sin el error multivar, con una prueba de regresión que cubra el ejemplo.