Update anchore/sbom-action action to v0.21.0

| datasource  | package             | from     | to      |
| ----------- | ------------------- | -------- | ------- |
| github-tags | anchore/sbom-action | v0.20.10 | v0.21.0 |


Signed-off-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/ci.yaml

@@ -97,7 +97,7 @@ jobs:
         if: github.event_name != 'pull_request'
 
       - name: Download Syft
-        uses: anchore/sbom-action/download-syft@fbfd9c6c189226748411491745178e0c2017392d # v0.20.10
+        uses: anchore/sbom-action/download-syft@a930d0ac434e3182448fe678398ba5713717112a # v0.21.0
         if: github.ref_type == 'tag'
 
       - name: Install Cosign