Update gru.md (#1152)
Update gru.md (#1152)

The key distinction between vanilla RNNs and GRUs is that the latter support gating of the hidden state.
翻译错误
mli/gluon-tutorials-zh,d2l-ai/d2l-zh,mli/gluon-tutorials-zh,mli/gluon-tutorials-zh,d2l-ai/d2l-zh,mli/gluon-tutorials-zh,d2l-ai/d2l-zh