Pin trivy to a specific SHA

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: VimukthiPerera

.github/workflows/terraform-scan.yml

@@ -21,7 +21,7 @@ jobs:
         uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
 
       - name: Run Trivy IaC scan
-        uses: aquasecurity/trivy-action@v0
+        uses: aquasecurity/trivy-action@d212fe86287abbcde3c51c3e86c52f14281a4a26 # v0.28.0
         with:
           scan-type: 'fs'
           scanners: 'misconfig'