fix(group): update the value when delete an item

[lzl0304]

Description

fixes #19655
fixes #19213

Markup:

<script setup>
  import { ref } from 'vue'

  const createItem = (title, hasValue = false) => ({
    id: Math.floor(Math.random() * 1000),
    title,
    content: '',
    value: hasValue ? Math.random().toString(16).slice(2) : undefined,
  })

  const items = ref([createItem('A'), createItem('B'), createItem('C')])

  const onAddItem = () => {
    items.value.push(createItem('D'))
  }

  const onDelete = (event, itemToBeDeleted) => {
    event.stopPropagation()
    const index = items.value.findIndex(item => item.id === itemToBeDeleted.id)
    items.value.splice(index, 1)
  }
</script>

<template>
  <v-app>
    <v-container>
      <v-expansion-panels class="accordion">
        <v-expansion-panel v-for="item in items" :key="item.id" :value="item.value">
          <v-expansion-panel-title>
            <template #actions="{ expanded }">
              <span class="">{{ `key: ${item.id}` }}</span>
              <v-icon
                :icon="expanded ? 'mdi-chevron-up' : 'mdi-chevron-down'"
                class="action"
              />
              <v-icon
                class="action delete"
                icon="mdi-delete"
                @click="event => onDelete(event, item)"
              />
            </template>
            <template #default="{ expanded }">
              <v-row no-gutters>
                <v-col class="d-flex justify-start" cols="11">
                  <v-text-field
                    v-model="item.title"
                    placeholder="Title"
                    variant="solo-filled"
                    hide-details
                  />
                </v-col>
              </v-row>
            </template>
          </v-expansion-panel-title>
          <v-expansion-panel-text>
            <v-row no-gutters>
              <v-col class="d-flex justify-start" cols="12">
                <v-textarea v-model="item.content" />
              </v-col>
            </v-row>
          </v-expansion-panel-text>
        </v-expansion-panel>
      </v-expansion-panels>
      <v-btn class="add-item-button" @click="onAddItem">
        <v-icon>mdi-plus</v-icon>
        Add item
      </v-btn>
    </v-container>
  </v-app>
</template>

<style>
.add-item-button {
  margin-top: 25px;
}
</style>