add upgrade to pip command (#1687)

Co-authored-by: Felipe Mello <[email protected]>

Author: felipemello1

README.md

@@ -119,8 +119,8 @@ pip install torchtune
 
 ```bash
 # Install PyTorch, torchvision, torchao nightlies
-pip install --pre torch torchvision torchao --index-url https://download.pytorch.org/whl/nightly/cu121
-pip install --pre torchtune --extra-index-url https://download.pytorch.org/whl/nightly/cpu
+pip install --pre --upgrade torch torchvision torchao --index-url https://download.pytorch.org/whl/nightly/cu121
+pip install --pre --upgrade torchtune --extra-index-url https://download.pytorch.org/whl/nightly/cpu
 ```
 
 You can also check out our [install documentation](https://pytorch.org/torchtune/main/install.html) for more information, including installing torchtune from source.