fix: use required: false rather than default: undefined for props

[danielroe]

🔗 Linked issue

❓ Type of change

• 📖 Documentation (updates to the documentation or readme)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

It feels like this might be a vue bug with prop type inference, but otherwise strange errors were occurring, e.g.:

<template>
  <NuxtImg
    v-if="uwuCookie"
    sizes="343px md:455px"
    width="455"
    height="256"
    class="mx-auto lg:my-16"
    src="/uwu.png"
    alt="Nuxt Logo in uwu style"
  />
</template>

pages/index.vue:86:9 - error TS2322: Type 'string' is not assignable to type 'undefined'.

86         sizes="343px md:455px"
           ~~~~~

https://github.com/nuxt/nuxt.com/actions/runs/10596463874/job/29364485513?pr=1650

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 61.95%. Comparing base (917242a) to head (e7de65c).
⚠️ Report is 563 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1450   +/-   ##
=======================================
  Coverage   61.95%   61.95%           
=======================================
  Files          79       79           
  Lines        3609     3609           
  Branches      391      393    +2     
=======================================
  Hits         2236     2236           
  Misses       1343     1343           
  Partials       30       30           

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