chore(deps): update dependency @netlify/serverless-functions-api to ^1.21.0 (#2551)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

Diff for: package-lock.json

@@ -55,7 +55,7 @@
     "@netlify/edge-functions": "^2.10.0",
     "@netlify/eslint-config-node": "^7.0.1",
     "@netlify/functions": "^2.8.1",
-    "@netlify/serverless-functions-api": "^1.20.0",
+    "@netlify/serverless-functions-api": "^1.21.0",
     "@netlify/zip-it-and-ship-it": "^9.37.3",
     "@opentelemetry/api": "^1.8.0",
     "@opentelemetry/exporter-trace-otlp-http": "^0.51.0",