bundle-uri: suppress stderr from remote-https

bundle-uri: suppress stderr from remote-https

When downloading bundles from a git-remote-https subprocess, the bundle
URI logic wants to be opportunistic and download as much as possible and
work with what did succeed. This is particularly important in the "any"
mode, where any single bundle success will work.

If the URI is not available, the git-remote-https process will die()
with a "fatal:" error message, even though that error is not actually
fatal to the super process. Since stderr is passed through, it looks
like a fatal error to the user.

Suppress stderr to avoid these errors from bubbling to the surface. The
bundle URI API adds its own warning() messages on these failures.

Signed-off-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>