Fix Protobuf<4.0 is deprecated, relax dependency

[hoh]

The last release was of protobuf <4 was version 3.20.3 in Sept 2022.

Problem

This dependency is not used in the project and causes conflicts in projects using a newer version.

The only reference to protobuf is here, and does not rely on the pinned version.

Proposal

Relax the dependency or remove it completely from pyproject.toml.

[danielhanchen]

Hmm I actually can't remember why I had protobuf - I think it was due to sentencepiece

[hoh]

Can it be removed instead then ?

[miguelamavel]

this requirement was relaxed in unsloth already #2637. can this be merged here too now?

[yxtay]

Is there any reason why protobuf is directly pinned in unsloth-zoo? The only reference in the code is the following, and it is to install an unpinned version of protobuf using pip.

unsloth-zoo/unsloth_zoo/llama_cpp.py

Line 295 in cfaaaa3

try_execute(f"{pip} install gguf protobuf sentencepiece", **kwargs)

If unsloth-zoo does not depend on protobuf directly, I'd recommend to completely remove specifying it as a dependency and allow downstream dependencies to install only if necessary.