Clean up README examples

[yeonsily]

What does this PR do?

Clean up README examples for old models.

Fixes # (issue)

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you make sure to update the documentation with your changes?
• Did you write any new necessary tests?

[xhaihao]

@yeonsily could you please add the example for baichuan2 back ? Baichuan2 is still in use.

[mengker33]

Hi @yeonsily , chatglm3-6b is recently added model and still in use, can you please keep it in README, thank you:)

[yeonsily]

@mengker33 @xhaihao Thanks for the review. If these models are still in use, can you please add them to CI test?

[xhaihao]

@yeonsily We have included Baichuan2 and chatglm3-6b in tests/test_text_generation_example.py. Could you please confirm if this is sufficient for the CI testing? Thank you very much!

[regisss]

@xhaihao @mengker33 I believe the goal of this PR is to simplify the READMEs as they contain many very similar commands. I think having concise READMEs is defintely a good thing, otherwise people will just not look at them.
Fine-tuning Baichuan and ChatGLM with DeepSpeed should still be pretty straightforward given that a few example commands are still given, unless there are specific arguments to use for these two models?

[libinta]

keep the above 3