selftests: fix typo in seccomp_bpf.c

There used to be an explanation here because it could trigger lockdep
previously, but now we're not doing recursive locking, so it really is just
for grins.

Signed-off-by: Tycho Andersen <tycho@tycho.ws>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Shuah Khan <shuah@kernel.org>