Fix workflow for publishing generic-ec-curves

Author: maurges

.github/workflows/publish.yml

@@ -46,6 +46,7 @@ jobs:
       github.ref_type == 'tag'
       && startsWith(github.ref_name, 'curves-v')
     steps:
+    - uses: actions/checkout@v3
     - run: cargo publish -p generic-ec-curves --token ${CRATES_TOKEN}
       env:
         CRATES_TOKEN: ${{ secrets.CRATES_TOKEN }}