ci: update slither config

Author: Luisfc68

.github/workflows/slither.yml

@@ -33,7 +33,7 @@ jobs:
           sarif: results.sarif
           fail-on: none
           target: .
-          slither-args: --filter-paths "node_modules/|contracts/test-contracts/safe-test-contracts/"
+          slither-args: --filter-paths "node_modules/|contracts/test-contracts/safe-test-contracts/|contracts/legacy"
       - name: Upload SARIF file
         uses: github/codeql-action/upload-sarif@48ab28a6f5dbc2a99bf1e0131198dd8f1df78169 # v3.28.0
         with: