Bump @grpc/grpc-js in /packages/auth-compat/demo/functions

Bumps [@grpc/grpc-js](https://github.com/grpc/grpc-node) from 1.6.7 to 1.8.21.
- [Release notes](https://github.com/grpc/grpc-node/releases)
- [Commits](https://github.com/grpc/grpc-node/compare/@grpc/grpc-js@1.6.7...@grpc/grpc-js@1.8.21)

---
updated-dependencies:
- dependency-name: "@grpc/grpc-js"
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <support@github.com>