fix(VTextarea): hide autoGrow scrollbar until maxRows is reached

[KaelWD]

Description

fixes #21982

Markup:

<template>
  <v-app>
    <v-container>
      <div style="width: 278px">
        <v-textarea
          :model-value="text"
          max-rows="9"
          rows="1"
          variant="filled"
          auto-grow
        />
      </div>
    </v-container>
  </v-app>
</template>

<script setup>
  const text = 'foo/bar/foo/bar/foo/bar/foo/bar '.repeat(8)
</script>

[J-Sek]

it makes it slightly inconsistent when textarea with auto-grow appears next to the regular one (without this prop heightCapped is always false and the *--height-capped is never present even though it has scrollbar, see playground).

[J-Sek]

I would drop thin and change none to:

&:not(.v-textarea--height-capped)
  .v-field__input
    scrollbar-width: none