remote-curl: die directly with http error messages

remote-curl: die directly with http error messages

When we encounter an unknown http error (e.g., a 403), we
hand the error code to http_error, which then prints it with
error(). After that we die with the redundant message "HTTP
request failed".

Instead, let's just drop http_error entirely, which does
nothing but pass arguments to error(), and instead die
directly with a useful message.

So before:

  $ git clone https://example.com/repo.git
  Cloning into 'repo'...
  error: unable to access 'https://example.com/repo.git': The requested URL returned error: 403 Forbidden
  fatal: HTTP request failed

and after:

  $ git clone https://example.com/repo.git
  Cloning into 'repo'...
  fatal: unable to access 'https://example.com/repo.git': The requested URL returned error: 403 Forbidden

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>