fix: replace deprecated method and add missing decorator

[nightosong]

Description

Changes:

1. method parse_obj is deprecated, use model_validate instead.
2. remove meaningless f-string format.
3. add missing classmethod decorator.

Snapshots:

Include snapshots for easier review.

Checklist:

• [X] My code follows the style guidelines of this project
• [X] I have already rebased the commits and make the commit message conform to the project standard.
• [X] I have performed a self-review of my own code
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [ ] Any dependent changes have been merged and published in downstream modules

[csunny]

@nightosong Thanks for your PR， can you fix the check errors? You can refer to https://github.com/eosphoros-ai/DB-GPT/blob/main/CONTRIBUTING.md

[csunny]

dbgpt/agent/core/action/base.py :184:89: E501 line too long (91 > 88 characters)

[nightosong]

@csunny The issue has been fixed. A recheck is needed.