Pinning min version of fh-llm-client

[jamesbraza]

The fh-llm-client added in #757 had an unpinned min version, which it turns out caused some problems downstream CI:

Installed 137 packages in 61ms
...
 + fh-llm-client==0.0.1
...

    from paperqa.agents.task import GradablePaperQAEnvironment, LitQAv2TaskDataset
.venv/lib/python3.11/site-packages/paperqa/__init__.py:3: in <module>
    from llmclient import (
E   ImportError: cannot import name 'EmbeddingModel' from 'llmclient'