Update safety API key reference in CI configuration

Author: josteinl

.github/workflows/branch.yaml

@@ -48,6 +48,6 @@ jobs:
       - name: Run safety
         run: uv run safety --disable-optional-telemetry --stage cicd scan
         env:
-          SAFETY_API_KEY: $(safety-api-key)
+          SAFETY_API_KEY: ${{ secrets.SAFETY_API_KEY }}
       - name: Check for acceptable licenses
         run: uv run pip-licenses --allow-only="MIT License;BSD License;Python Software Foundation License;Apache Software License;Mozilla Public License 2.0 (MPL 2.0);The Unlicense (Unlicense);ISC License (ISCL)"