[quantization] Fix deepcopy on quantized ConvNd (#56154)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/56154
Test Plan: Imported from OSS
Reviewed By: vkuzo
Differential Revision: D27796268
Pulled By: jamesr66a
fbshipit-source-id: cb693dc16582a9334c93f46201c42eb0f4b794b3
