Provide an alternative clone instructions. (#957)

Summary:
Pull Request resolved: #957

.

Reviewed By: dbort

Differential Revision: D50333814

fbshipit-source-id: 51159b685eb29e5c446590c564836cd9bff29fac

Author: shoumikhin

docs/source/getting-started-setup.md

@@ -86,7 +86,7 @@ Follow these steps:
 1. Clone the `executorch` repository:
 
    ```bash
-   git clone --branch v0.1.0 git@github.com:pytorch/executorch.git
+   git clone --branch v0.1.0 https://github.com/pytorch/executorch.git
    ```
 
 1. Update the submodules: