Refine ChatModelAgent description in documentation

[CXeon]

Corrected minor grammatical errors and improved clarity in the explanation of ChatModelAgent's functionalities.

What type of PR is this?

Check the PR title.

• This PR title match the format: <type>(optional scope): <description>
• The description of this PR title is user-oriented and clear enough for others to understand.

(Optional) Translate the PR title into Chinese.

(Optional) More detailed description for this PR(en: English/zh: Chinese).

en:
zh(optional):

(Optional) Which issue(s) this PR fixes:

[netlify]

✅ Deploy Preview for cloudwego ready!

Name	Link
🔨 Latest commit	256b496
🔍 Latest deploy log	https://app.netlify.com/projects/cloudwego/deploys/6969f173929a0d000843bd18
😎 Deploy Preview	https://deploy-preview-1497--cloudwego.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}