fix for resize to 224 when training AlextNet in alexnet-gluon.md
fix for resize to 224 when training AlextNet in alexnet-gluon.md

mli/gluon-tutorials-zh,d2l-ai/d2l-zh,mli/gluon-tutorials-zh,mli/gluon-tutorials-zh,mli/gluon-tutorials-zh,d2l-ai/d2l-zh,d2l-ai/d2l-zh