🐛 [BUG]雷达图开启meta.formatter就会导致日期字符串变成时间戳

### 🐛 Bug description [Please make everyone to understand it]

> Please provide a link by forking these links [G2Plot](https://codesandbox.io/s/g2plot-issue-template-gzfdq?file=/index.ts) or GitHub repo, a minimal reproduction.

* _Required_ **Link to minimal reproduction**:

### 📷 Step to reproduce
https://codesandbox.io/s/cold-https-ejbz5b?file=/index.ts
### 🏞 Expected result

### 🚑 Any additional [like screenshots]

* **G2Plot Version**:
* **Platform**:

Start with the linked CodeSandbox reproduction and verify the radar chart behavior when meta.formatter is enabled. Trace the formatter handling responsible for converting date strings to timestamps. Done means the reproduction preserves date strings while the formatter remains enabled.

Written by the indexing model from the issue text.