Fix security issue: pin TruffleHog action to specific version

Co-authored-by: thoughtparametersllc <194255310+thoughtparametersllc@users.noreply.github.com>

Author: Copilot

.github/workflows/security-audit.yml

@@ -126,7 +126,7 @@ jobs:
           fetch-depth: 0
 
       - name: TruffleHog OSS
-        uses: trufflesecurity/trufflehog@main
+        uses: trufflesecurity/trufflehog@v3.90.12
         with:
           path: ./
           base: ${{ github.event.repository.default_branch }}