fix(VRadioGroup): remove multiple prop

[jacekkarczmarczyk]

Description

Removes multiple prop

There are some other props that are passed as attr to VSelectionControlGroup (density, error, ripple, valuecomparator), not sure if they should just be removed from props or somehow handled

Motivation and Context

fixes #15559

How Has This Been Tested?

yarn test + apigen

Markup

<template>
  <v-main>
    <v-radio-group multiple>
      <v-radio value="1" label="1" />
      <v-radio value="2" label="2" />
    </v-radio-group>
  </v-main>
</template>

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Improvement/refactoring (non-breaking change that doesn't add any features but makes things better)

Checklist:

• The PR title is no longer than 64 characters.
• The PR is submitted to the correct branch (master for bug fixes and documentation updates, dev for new features and backwards compatible changes and next for non-backwards compatible changes).
• My code follows the code style of this project.
• I've added relevant changes to the documentation (applies to new features and breaking changes in core library)

[KaelWD]

I kinda hate this but everything else I can think of is even worse

other props

Should probably be added to VSelectionControlGroup and provided like the radio props are