libbpf: Start v1.3 development cycle

Bump libbpf.map to v1.3.0 to start a new libbpf version cycle.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20230523170013.728457-3-andrii@kernel.org