io_jail: remove unused c_long import
io_jail: remove unused c_long import

This is no longer used after the bindings were updated to use c_ulong
instead of c_long; remove it to fix a compiler warning.

BUG=None
TEST=cargo build

Change-Id: I813b06797ddc8b6cdfd8b777bd0a6efe6ec914a4
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2047643
Reviewed-by: Stephen Barber <7719587e4b5a49340661b214ec85602f3918d06f@chromium.org>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Commit-Queue: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>

google/crosvm,google/crosvm,google/crosvm,google/crosvm