Fully Convolutional Networks (FCN)

http://en.diveintodeeplearning.org/chapter_computer-vision/fcn.html

In section 12.11.2, line number 4, correct the spelling of “thee”

Thanks and fixed! https://github.com/d2l-ai/d2l-en/commit/60dc354f8dc05769c3439a0efd9ae30ef61c3407