Bump protobufjs from 6.11.3 to 6.11.4 in /packages/demo

Bumps [protobufjs](https://github.com/protobufjs/protobuf.js) from 6.11.3 to 6.11.4.
- [Release notes](https://github.com/protobufjs/protobuf.js/releases)
- [Changelog](https://github.com/protobufjs/protobuf.js/blob/master/CHANGELOG.md)
- [Commits](https://github.com/protobufjs/protobuf.js/commits)

---
updated-dependencies:
- dependency-name: protobufjs
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <[email protected]>