A trivial error message updates on `at::Tensor _convolution` (#15830)
Summary:
I fixed an grammatical error on this function previously, but I also realized that its content was also wrong. A weight tensors of a convolutional layer should be at least 3 dimensional, not 2.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/15830
Differential Revision: D13597968
Pulled By: soumith
fbshipit-source-id: 72a75106e88945c68d6462828b149441cfb5acde
