🐛 [BUG] Mix多图层图表缩略轴无法自适应图表宽度

### 🐛 Bug description
Mix多图层图表缩略轴无法自适应图表宽度

> 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**: https://codesandbox.io/s/5ychjl

### 📷 Step to reproduce
- 使用Mix图表，打开缩略轴，
- 假设初始宽度为300px，拖动宽度为500的时候
- 缩略轴的宽度还是图表拖动前的宽度

### 🏞 Expected result
- 期望结果：自适应

### 🚑 Any additional [like screenshots]

* **G2Plot Version**: 2.3.40
* **Platform**:

Start with index.ts in the linked CodeSandbox minimal reproduction and reproduce the Mix chart behavior in G2Plot 2.3.40 by resizing it from 300px to 500px with the thumbnail axis enabled. Trace the Mix chart and thumbnail-axis entry points to determine where the stale width is retained; done means the thumbnail axis adapts to the chart's new width.

Written by the indexing model from the issue text.