chore(zizmor): update shared-workflows ref to include PR comment fallback (#153)

Update the reusable-zizmor.yml reference to pick up:
- PR comment is now a fallback for private repos without Advanced Security
  (public repos only get Code Scanning annotations, reducing noise)
- zizmor updated from 1.23.1 to 1.24.1 (improved SARIF codeflows,
  bug fixes)

See: grafana/shared-workflows#1876

Author: Duologic

.github/workflows/self-zizmor.yaml

@@ -45,7 +45,7 @@ jobs:
       - zizmor-check
     if: ${{ needs.zizmor-check.outputs.found-files == 'true' }}
 
-    uses: grafana/shared-workflows/.github/workflows/reusable-zizmor.yml@9099825d5ef82fa57e0cf6a263477bc926f51bfa
+    uses: grafana/shared-workflows/.github/workflows/reusable-zizmor.yml@5cec40ba1a943db268a9bb33f208c006b161d372
     with:
       runs-on: ${{ !github.event.repository.private && 'ubuntu-latest' || 'ubuntu-arm64-small' }}
       fail-severity: high