In particular, this means that 'guix lint' won't warn to update to
versions that won't necessarily fit our package set well.
* guix/import/stackage.scm (%stackage-url): Change to "https",
avoiding redirect log messages.
(%default-lts-version): New variable.
(stackage-lts-info-fetch, stackage->guix-package,
latest-lts-release): Use it.
(lts-info-ghc-version): Remove unused procedure.
Signed-off-by: Timothy Sample <samplet@ngyro.com>