Doc: remove line saying that 4Dx2D tensor multiplication is supported.
Doc: remove line saying that 4Dx2D tensor multiplication is supported.

Currently TensorOperator only supports 1Dx1D, 2Dx1D, and 2Dx2D tensor
multiplication.

yozw/torch7,clementfarabet/torch7,szagoruyko/torch7,wickedfoo/torch7,diz-vara/torch7,wgapl/torch7,colesbury/torch7,Moodstocks/torch7,Atcold/torch7,diz-vara/torch7,Moodstocks/torch7,wgapl/torch7,nicholas-leonard/torch7,nicholas-leonard/torch7,clementfarabet/torch7,Atcold/torch7,szagoruyko/torch7,wickedfoo/torch7,adamlerer/torch7,colesbury/torch7,yozw/torch7,adamlerer/torch7