Add 'git checkout' to working state of repo

Author: kkawula

.github/workflows/checks.yml

@@ -197,6 +197,8 @@ jobs:
           options: --rm -v ${{ github.workspace }}:/apps
           run: |
             cd /apps/app-starknet
+            git checkout 911c28953d0f14859639cafa750f3d00e94a1be3
+            git switch -c working-state
             cargo clean
             cargo ledger build nanox