Documentation: kernel-parameters: remove noaliencache

Since slab allocator has already been removed. There is no users of
the noaliencache parameter, so let's remove it.

Suggested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Xiongwei Song <xiongwei.song@windriver.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>