bpftool: Add HELP_SPEC_OPTIONS in token.c

$ ./bpftool token help

Usage: bpftool token { show | list }
       bpftool token help
       OPTIONS := { {-j|--json} [{-p|--pretty}] | {-d|--debug} }

Fixes: 2d812311 ("bpftool: Add bpf_token show")
Signed-off-by: Tao Chen <chen.dylane@linux.dev>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Quentin Monnet <qmo@kernel.org>
Link: https://lore.kernel.org/bpf/20250919034816.1287280-1-chen.dylane@linux.dev