ci: fetch tag name on release

Signed-off-by: Ricardo Lopes <[email protected]>

Author: ricardoapl

.github/workflows/sbom.yaml

@@ -16,8 +16,8 @@ jobs:
       contents: write
 
     env:
-      OUTPUT: kube-state-metrics-${{ github.ref_name }}.spdx
-      TAG: ${{ github.ref_name }}
+      OUTPUT: kube-state-metrics-${{ github.event.release.tag_name }}.spdx
+      TAG: ${{ github.event.release.tag_name }}
 
     steps:
       - name: Fetch source code into GITHUB_WORKSPACE