bpftool: Fix a typo in a comment

This is the wrong library name: libcap, not libpcap.

Signed-off-by: Quentin Monnet <quentin@isovalent.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220812153727.224500-1-quentin@isovalent.com