sync: Update libbpf submodule

Pull latest libbpf from mirror.
Libbpf version: 1.4.0
Libbpf commit:  f81eef23b33c0dbf923e863a72ce51ea4d32e291

Signed-off-by: Quentin Monnet <[email protected]>
diff --git a/libbpf b/libbpf
index 20c0a9e..f81eef2 160000
--- a/libbpf
+++ b/libbpf
@@ -1 +1 @@
-Subproject commit 20c0a9e3d7e7d4aeb283eae982543c9cacc29477
+Subproject commit f81eef23b33c0dbf923e863a72ce51ea4d32e291