fix(ci): use zama-bot keys to fetch other repo

.github/workflows/rust.yml

@@ -24,7 +24,7 @@ jobs:
       # A SSH private key is required as some dependencies are from private repos
       - uses: webfactory/ssh-agent@v0.5.2
         with:
-          ssh-private-key: ${{ secrets.SSH_PRIVATE_KEY2 }}
+          ssh-private-key: ${{ secrets.CONCRETE_COMPILER_CI_SSH_PRIVATE }}
 
       - name: cargo check
         uses: actions-rs/cargo@v1