Update README.md

update readme.md for PaddleST

PaddleST/Research/README.md

-## PaddleST for Research
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-- Provide the codes and the datasets of the latest research based on large-scale spatial-temporal data.
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-- Enable the developers and researchers to easily reproduce the experiments of the published academic papers and quickly develop their new methods.
+This work has been moved to new address: [PaddleST](https://github.com/PaddlePaddle/Research/tree/master/ST_DM)