[TextField] Remove scrollbars with verticalContent (#11270)

### WHY are these changes introduced?

Fixes #9061

### WHAT is this pull request doing?

This removes the visible scrollbars in the `TextField` component when
using `verticalContent`, which were causing a less than ideal visual
appearance. The solution used was to change `overflow: scroll` to
`overflow: auto` so that scrollbars only display when needed.

<details>
  <summary>Before</summary>
  <img src="https://screenshot.click/01-12-xarq1-p4nx8.png">
</details>

<details>
  <summary>After</summary>
  <img src="https://screenshot.click/01-11-kg4v2-7qb6a.png">
</details>

Author: moraleslevi

.changeset/fifty-chicken-lay.md

@@ -0,0 +1,5 @@
+---
+'@shopify/polaris': patch
+---
+
+Remove scrollbars from TextField vertical content

polaris-react/src/components/TextField/TextField.scss

@@ -343,7 +343,7 @@ $spinner-icon-size: 12px;
   color: var(--p-color-text-secondary);
   padding: var(--p-space-200) var(--p-space-200) 0 var(--p-space-200);
   max-height: 140px;
-  overflow: scroll;
+  overflow: auto;
   border: var(--p-border-width-025) solid transparent;
   width: 100%;