Bump protobufjs from 5.0.0 to 6.8.8 in /HW/machinetalk-protobuf

Bumps [protobufjs](https://github.com/dcodeIO/protobuf.js) from 5.0.0 to 6.8.8.
- [Release notes](https://github.com/dcodeIO/protobuf.js/releases)
- [Changelog](https://github.com/protobufjs/protobuf.js/blob/master/CHANGELOG.md)
- [Commits](protobufjs/protobuf.js@5.0.0...6.8.8)

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

Author: dependabot[bot]

HW/machinetalk-protobuf/package.json

@@ -24,7 +24,7 @@
   "homepage": "https://github.com/machinekit/machinetalk-protobuf#readme",
   "dependencies": {
     "mkdirp": "0.5.1",
-    "protobufjs": "5.0.0"
+    "protobufjs": "6.8.8"
   },
   "devDependencies": {
     "browserify": "^13.0.0",