Fix documentation of minimum function.
Fix documentation of minimum function.

chainer/chainer,cupy/cupy,kikusu/chainer,aonotas/chainer,jnishi/chainer,wkentaro/chainer,niboshi/chainer,okuta/chainer,okuta/chainer,kikusu/chainer,ktnyt/chainer,keisuke-umezawa/chainer,cupy/cupy,ktnyt/chainer,wkentaro/chainer,cupy/cupy,okuta/chainer,okuta/chainer,niboshi/chainer,jnishi/chainer,niboshi/chainer,wkentaro/chainer,kashif/chainer,wkentaro/chainer,keisuke-umezawa/chainer,chainer/chainer,ktnyt/chainer,keisuke-umezawa/chainer,jnishi/chainer,tkerola/chainer,jnishi/chainer,cupy/cupy,rezoo/chainer,anaruse/chainer,hvy/chainer,ysekky/chainer,ronekko/chainer,delta2323/chainer,pfnet/chainer,hvy/chainer,kiyukuta/chainer,niboshi/chainer,keisuke-umezawa/chainer,ktnyt/chainer,hvy/chainer,hvy/chainer,chainer/chainer,chainer/chainer