fix(VDataTable): emit current items immediately

[J-Sek]

Description

Follow-up on a2f16f4 from 8 months ago. immediate: true was used in V2 (VData.ts - line 266), but it was not obvious from the wording in the documentation. I think it was not intentional to write watch without it.

fixes #20440

Markup:

<template>
  <v-data-table
    :headers="headers"
    :items="items"
    @update:current-items="console.log('current-items', $event)"
  />
</template>

<script setup>
  const headers = [
    { title: 'Vegetable', key: 'name' },
    { title: 'Calories', key: 'calories' },
    { title: 'Fat (g)', key: 'fat' },
    { title: 'Carbs (g)', key: 'carbs' },
    { title: 'Protein (g)', key: 'protein' },
  ]
  const items = Array.from({ length: 50 }).map((_, i) => ({
    name: `Item #${i}`,
    calories: (Math.random() * 300).toFixed(),
    fat: (Math.random() * 60).toFixed(1),
    carbs: (Math.random() * 100).toFixed(),
    protein: (Math.random() * 40).toFixed(),
  }))
</script>

[Kinco-dev]

Thanks @J-Sek
Hope it will be published soon