fix: use ssh to clone private git repos in sandboxes

assets/sbx-kit/spec.yaml

@@ -318,11 +318,6 @@ setup:
         fi
       user: '0'
       description: Configure SSH commit signing with a dynamic key command
-    - command: |
-        git config --system url."https://github.com/".insteadOf "git@github.com:"
-        git config --system --add url."https://github.com/".insteadOf "ssh://git@github.com/"
-      user: '0'
-      description: Route SSH GitHub remotes through HTTPS so the proxy can inject credentials
 
   startup:
     - command: