Bump protobuf from 5.1.0 to 6.0.0 in the pub group

Bumps the pub group with 1 update: [protobuf](https://github.com/google/protobuf.dart).


Updates `protobuf` from 5.1.0 to 6.0.0
- [Release notes](https://github.com/google/protobuf.dart/releases)
- [Commits](google/protobuf.dart@protobuf-v5.1.0...protobuf-v6.0.0)

---
updated-dependencies:
- dependency-name: protobuf
  dependency-version: 6.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: pub
...

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

Author: dependabot[bot]

pubspec.yaml

@@ -12,7 +12,7 @@ dependencies:
   http: '>=0.13.0 <2.0.0'
   logging: ^1.0.0
   meta: '>=1.9.1 <2.0.0'
-  protobuf: ">=2.0.0 <6.0.0"
+  protobuf: ">=2.0.0 <7.0.0"
   quiver: '>=3.0.0 <4.0.0'
 
 dev_dependencies: