fix(VSpeedDial): Use content-class

[J-Sek]

Description

content-class is mentioned by VSpeedDial API docs and should be applied down to the VMenu.

resolves #20051

Markup:

<template>
  <v-card class="pa-6">
    <v-fab size="large" icon>
      <v-icon>mdi-comment</v-icon>
      <v-speed-dial
        v-model="fabOpen"
        :content-class="['bg-grey-lighten-3','rounded-pill','elevation-2','pa-2']"
        activator="parent"
        location="right center"
      >
        <v-btn key="1" color="success" icon="$success" />
        <v-btn key="2" color="info" icon="$info" />
        <v-btn key="3" color="warning" icon="$warning" />
        <v-btn key="4" color="error" icon="$error" />
      </v-speed-dial>
    </v-fab>
  </v-card>
</template>

<script setup>
  import { ref } from 'vue'
  const fabOpen = ref(true)
</script>