Previously it would try to access the real elpa.gnu.org. This would
succeed when network is available because "taxy-magit-section" is an
existing package.
* guix/import/elpa.scm (elpa-repository)
(package-from-elpa-repository?): Recognize 'gnu/http.
* tests/elpa.scm ("package-latest-release"): Use 'http' instead of
'https'. Change "taxy-magit-section" to "fake-taxy-magit-section".