gha: don't forget to checkout before calling release script from the repo

.github/workflows/c-cpp.yml

@@ -117,6 +117,8 @@ jobs:
     needs: [build, flatpak]
     if: ${{ github.event_name == 'push' }}
     steps:
+    - name: Checkout
+      uses: actions/checkout@v4
     - name: Remove old release, fetch artifacts, repackage binaries and upload new release
       env:
         GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}