value_box value is too small

```python
x.ui.value_box("model_1", "0.98")
```

<img width="166" alt="image" src="https://github.com/rstudio/py-shiny/assets/129551/39e062a5-4f94-4046-8327-61a8b4ab7cb6">

This is different than the R version of this function. The reason is because in Python, "0.98" is going in without an enclosing tag, while in R, a bare string is wrapped in `<p></p>`.