bpftool: Fix typo in usage help

The usage help for "bpftool prog help" contains a ° instead of the _
symbol for cgroup/sendmsg_unix. Fix the typo.

Fixes: 8b3cba98 ("bpftool: Add support for cgroup unix socket address hooks")
Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Quentin Monnet <qmo@kernel.org>
Link: https://lore.kernel.org/bpf/20240717134508.77488-1-donald.hunter@gmail.com

tools/bpf/bpftool/prog.c

@@ -2489,7 +2489,7 @@ static int do_help(int argc, char **argv)
 		"                 cgroup/connect_unix | cgroup/getpeername4 | cgroup/getpeername6 |\n"
 		"                 cgroup/getpeername_unix | cgroup/getsockname4 | cgroup/getsockname6 |\n"
 		"                 cgroup/getsockname_unix | cgroup/sendmsg4 | cgroup/sendmsg6 |\n"
-		"                 cgroup/sendmsg°unix | cgroup/recvmsg4 | cgroup/recvmsg6 | cgroup/recvmsg_unix |\n"
+		"                 cgroup/sendmsg_unix | cgroup/recvmsg4 | cgroup/recvmsg6 | cgroup/recvmsg_unix |\n"
 		"                 cgroup/getsockopt | cgroup/setsockopt | cgroup/sock_release |\n"
 		"                 struct_ops | fentry | fexit | freplace | sk_lookup }\n"
 		"       ATTACH_TYPE := { sk_msg_verdict | sk_skb_verdict | sk_skb_stream_verdict |\n"