samples/bpf: fix tcp_bpf.readme detach command

Copy-paste, should be detach, not attach.
Signed-off-by: NStanislav Fomichev <sdf@google.com>
Acked-by: NSoheil Hassas Yeganeh <soheil@google.com>
Acked-by: NYuchung Cheng <ycheng@google.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>

samples/bpf/tcp_bpf.readme

@@ -25,4 +25,4 @@ attached to the cgroupv2).
 
 To remove (unattach) a socket_ops BPF program from a cgroupv2:
 
-  bpftool cgroup attach /tmp/cgroupv2/foo sock_ops pinned /sys/fs/bpf/tcp_prog
+  bpftool cgroup detach /tmp/cgroupv2/foo sock_ops pinned /sys/fs/bpf/tcp_prog