fix(VSparkline): fix duplicate id on VSparkline path

[adrienbaron]

Description

This MR removes the id property on the SVG path element from VSparkline.

Motivation and Context

VSparkline has a duplicated id. It uses the same id for it's path element and the linearGradient.
This creates an issue during SSR rehydration where the path disappear as it can't find the gradient.

How Has This Been Tested?

This has been tested visually to check it's still renders properly. The snapshots have also been updated.
I haven't been able to link my local Vuetify to a Nuxt project to check removing the duplicated id does fix the issue, however it seems very likely it will.

Markup:

<template>
  <v-container>
    <v-sparkline
      auto-draw
      :value="[0, 2, 5, 9, 5, 10, 3, 5, 0, 0, 1, 8, 2, 9, 0]"
      :gradient="['#623195', '#9e6dd1']"
      :line-width="2"
    />
  </v-container>
</template>

<script>
  export default {
    data: () => ({
    //
    }),
  }
</script>

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)