Install torchgen for Windows ARM64 codegen

Author: JacobSzwejbka

.github/workflows/windows-msvc.yml

@@ -89,7 +89,7 @@ jobs:
 
       - name: Install build dependencies
         shell: pwsh
-        run: python -m pip install pyyaml
+        run: python -m pip install pyyaml torch==2.13.0 --extra-index-url https://download.pytorch.org/whl/test/cpu
 
       - name: Build ExecuTorch
         shell: pwsh