build: remove the sched gnulib module

The 'sched' module provides a sched.h header file for platforms which
lack it. We already check for the functions we need in configure, and
protect the use of sched.h where relevant, so don't need the compat
header in libvirt.
Reviewed-by: NJán Tomko <jtomko@redhat.com>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

bootstrap.conf

@@ -74,7 +74,6 @@ posix-shell
 pthread_sigmask
 recv
 regex
-sched
 send
 setenv
 setsockopt