remote-curl: Fix Accept header for smart HTTP connections

remote-curl: Fix Accept header for smart HTTP connections

We actually expect to see an application/x-git-upload-pack-result
but we lied and said we Accept *-response.  This was a typo on my
part when I was writing the code.

Fortunately the wrong Accept header had no real impact, as the
deployed git-http-backend servers were not testing the Accept
header before they returned their content.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>