Setup.py > underscores to hyphens fix

[marklysze]

Why are these changes needed?

pip install does not allow underscores in the package extras, so the graph_rag_falkor_db extra is being interpreted as graph-rag-falkor-db and can't be found in the setup.py.

This fixes that by changing it to hyphens so they can install either:
pip install ag2[graph_rag_falkor_db] or pip install ag2[graph-rag-falkor-db]

Related issue number

Discord issue

Checks

• I've included any doc changes needed for https://ag2ai.github.io/ag2/. See https://ag2ai.github.io/ag2/docs/Contribute#documentation to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[AgentGenie]

Nice one.
Could you comment with the information right above this section in the file?

[AgentGenie]

LGTM!