🐛 [Bug]: 按照文档，中ConfigProvider 的 修改主题颜色的方式，修改Picker 中选中选项的 字体颜色，不生效

[tingfeima]

Which React Vant packages are impacted?

• react-vant (React Vant core)
• react-vant-icons(React Vant Icon)

What version of React Vant are you using?

3.3.5

Reproduce live demo(codesandebox or stackblitz)?

No response

Descripition

import React, { useState } from 'react'
import isEmpty from 'lodash/isEmpty'
import { ConfigProvider, Picker, Field } from 'react-vant'
import { fieldNamesData } from '../utils/cityData'

export default ({ handleArea, area }) => {
let defaultCity = ['北京市', '北京市', '东城区']
let preCity = null
if (area) {
preCity = area.split('，').filter((o) => o)
defaultCity = preCity
}
const [value, setValue] = useState(defaultCity)
return (
<ConfigProvider
themeVars={{
rvPickerOptionTextColor: '#FF4901',
// '--rv-picker-option-text-color': '#FF4901',
// '--rv-picker-option-text-color--selected': '#FF4901',
}}
>
<Picker
confirmButtonText={
<span
style={{
color: '#FF4901',
fontSize: '16px',
lineHeight: '20px',
}}
>
确定

}
cancelButtonText={
<span
style={{
color: '#666',
fontSize: '16px',
lineHeight: '20px',
}}
>
取消

}

    itemHeight={44}
    visibleItemCount={4}
    popup={{
      round: true,
    }}
    value={value}
    placeholder={''}
    columns={fieldNamesData}
    columnsFieldNames={{
      text: 'cityName',
      children: 'cities',
    }}
    onConfirm={(v) => {
      setValue(v)
      handleArea(v.join('，'))
    }}
  >
    {(val, _, actions) => {
      return (
        <Field
          isLink={true}
          style={{ color: '#999' }}
          readOnly
          clickable
          controlAlign="right"
          value={isEmpty(preCity) ? preCity : val || ''}
          placeholder="选择城市"
          onClick={() => actions.open()}
        />
      )
    }}
  </Picker>
</ConfigProvider>

)
}