MAINTAINERS: remove Zefan Li

Not active for a long time, so remove myself from MAINTAINERS.

Cc: Zefan Li <lizefan.x@bytedance.com>
Signed-off-by: Zefan Li <lizf.kern@gmail.com>
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Tejun Heo <tj@kernel.org>