update installation instructions [skip ci]

Author: rusty1s

README.md

@@ -47,7 +47,7 @@ We provide pip wheels for all major OS/PyTorch/CUDA combinations, see [here](htt
 To install the binaries for PyTorch 1.7.0, simply run
 
 ```
-pip install torch-scatter==latest+${CUDA} -f https://pytorch-geometric.com/whl/torch-1.7.0.html
+pip install torch-scatter -f https://pytorch-geometric.com/whl/torch-1.7.0+${CUDA}.html
 ```
 
 where `${CUDA}` should be replaced by either `cpu`, `cu92`, `cu101`, `cu102`, or `cu110` depending on your PyTorch installation.
@@ -63,7 +63,7 @@ where `${CUDA}` should be replaced by either `cpu`, `cu92`, `cu101`, `cu102`, or
 To install the binaries for PyTorch 1.6.0, simply run
 
 ```
-pip install torch-scatter==latest+${CUDA} -f https://pytorch-geometric.com/whl/torch-1.6.0.html
+pip install torch-scatter -f https://pytorch-geometric.com/whl/torch-1.6.0+${CUDA}.html
 ```
 
 where `${CUDA}` should be replaced by either `cpu`, `cu92`, `cu101` or `cu102` depending on your PyTorch installation.