Update version for wheels and docs (#3984)

Author: lucylq

.github/workflows/build-wheels-linux.yml

@@ -19,7 +19,7 @@ on:
 
 jobs:
   generate-matrix:
-    uses: pytorch/test-infra/.github/workflows/generate_binary_build_matrix.yml@main
+    uses: pytorch/test-infra/.github/workflows/generate_binary_build_matrix.yml@release/0.3.0
     with:
       package-type: wheel
       os: linux

docs/source/getting-started-setup.md

@@ -89,7 +89,7 @@ To utilize ExecuTorch to its fullest extent, please follow the setup instruction
 
    ```bash
    # Clone the ExecuTorch repo from GitHub
-   git clone https://github.com/pytorch/executorch.git
+   git clone --branch v0.3.0 https://github.com/pytorch/executorch.git
    cd executorch
 
    # Update and pull submodules