chore: update underline select padding (#170)

Sorry for the dual PR. Follow up for
#168

I believe `pr-10` should be applied for consistency.
[explanation](#168 (comment))

Also, the updated `index.html` does not seems to be deployed to
production.

https://tailwindcss-forms.vercel.app/

index.html

@@ -157,7 +157,7 @@ <h2 class="text-2xl font-bold">Underline</h2>
  <label class="block">
  <span class="text-gray-700">What type of event is it?</span>
  <select
- class="mt-0 block w-full border-0 border-b-2 border-gray-200 pl-0.5 pr-7 focus:border-black focus:ring-0"
+ class="mt-0 block w-full border-0 border-b-2 border-gray-200 pl-0.5 pr-10 focus:border-black focus:ring-0"
  >
  <option>Corporate event</option>
  <option>Wedding</option>