TRIVIAL: fix typo in github action

Author: svenRelovsky

.github/workflows/docker.yml

@@ -47,4 +47,4 @@ jobs:
       - name: Sign the images
         env:
           DIGEST: ${{ steps.build.outputs.digest }}
-        run: cosign sign --yes "${{ env.REGISTRY }}//${{ env.IMAGE_NAME }}@${DIGEST}"
+        run: cosign sign --yes "${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}@${DIGEST}"