libbpf: Start v1.4 development cycle

Bump libbpf.map to v1.4.0 to start a new libbpf version cycle.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20231123000439.12025-1-eddyz87@gmail.com