Fix typo in docstring of elu function
Fix typo in docstring of elu function

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