ci: fix image signature

Author: sandhose

.github/workflows/ci.yaml

@@ -397,9 +397,9 @@ jobs:
           github.event_name != 'pull_request'
           && (startsWith(github.ref, 'refs/tags/v') || github.ref == 'refs/heads/main')
 
-        run: >
-          cosign sign
-            "${{ env.IMAGE }}@${{ fromJSON(steps.bake.outputs.metadata).regular['containerimage.digest'] }}"
+        run: |
+          cosign sign \
+            "${{ env.IMAGE }}@${{ fromJSON(steps.bake.outputs.metadata).regular['containerimage.digest'] }}" \
             "${{ env.IMAGE }}@${{ fromJSON(steps.bake.outputs.metadata).debug['containerimage.digest'] }}"
         env:
           COSIGN_EXPERIMENTAL: 1