Update installation instructions to point to new releases page.

README.md

@@ -45,7 +45,7 @@ python -m venv mlir_venv
 source mlir_venv/bin/activate
 # Some older pip installs may not be able to handle the recent PyTorch deps
 python -m pip install --upgrade pip
-pip install --pre torch-mlir torchvision -f https://github.com/llvm/torch-mlir/releases --extra-index-url https://download.pytorch.org/whl/nightly/cpu
+pip install --pre torch-mlir torchvision -f https://llvm.github.io/torch-mlir/package-index/ --extra-index-url https://download.pytorch.org/whl/nightly/cpu
 # This will install the corresponding torch and torchvision nightlies
 ```