fix(VSparkline): accept numeric value for smooth

[J-Sek]

Description

fixes #19262

Markup:

<template>
  <v-app>
    <v-container>
      <v-sparkline :model-value="values" :smooth="4" />
      <v-sparkline :model-value="values" smooth />
      <v-sparkline :model-value="values" smooth="1" />
      <v-sparkline :model-value="values" :smooth="1" />
    </v-container>
  </v-app>
</template>

<script setup>
  const values = [80, 75, 60, 55, 65, 60, 62, 58, 55, 65, 60, 68, 62, 58, 65, 70, 65, 75, 70]
</script>