fix(VOtpInput): slice value with length on paste

[SonTT19]

Description

fixes #20158

Markup:

<template>
  <v-app>
    <v-container>
      // Copy and paste: 12345678
      <v-otp-input v-model="otp" :length="5" />
      Value: {{ otp }}
    </v-container>
  </v-app>
</template>

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

  const otp = ref('')
</script>