Protobuf 6 support

[clovisNyu]

🚀 Feature

Bump protobuf dependency to 6

Motivation

Currently, the protobuf dependency is set to version 4. This was deprecated in Q1 2025.

Alternatives

We could also use protobuf version 5, as at least it has not reached End of Life yet.

Additional context

When trying to use the library with opentelemetry, I end up with version conflict on protobuf. Is it possible to upgrade to the latest version of protobuf?

[gblazq]

I'm also having issues with conflicts due to the protobuf pin.

I'm wondering if the dependency is even needed, it doesn't seem like the project uses it, and according to poetry show protobuf no other package requires it. Also, the tests pass without it.

I can prepare a small PR if it's OK to remove the dependency pin.