A trivial error in the error message of `at::Tensor _convolution` fixed (#15772)
Summary:
A trivial grammatical error fix.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/15772
Differential Revision: D13592279
Pulled By: zou3519
fbshipit-source-id: 14f60c61747a3893cd0e4c860f7b4c4c4ba28c28
