[Docs] Update instruction to OST dataset
update instruction to OST Datasets
- The DIV2K dataset can be downloaded from [here](https://data.vision.ee.ethz.ch/cvl/DIV2K/) (We use the training set only).
- The Flickr2K dataset can be downloaded [here](https://cv.snu.ac.kr/research/EDSR/Flickr2K.tar) (We use the training set only).
-- The OST dataset can be downloaded [here](https://github.com/xinntao/SFTGAN#ost-dataset) (We use the training set only).
+- The OST dataset can be downloaded [here](https://github.com/xinntao/SFTGAN#ost-dataset) (We use the training set OutdoorSceneTrain_v2 only).
Please first put all the images into the `GT` folder (naming does not need to be in order):
