fix(ui): remove vertical scrollbar (#101243)

the message gets rendered as a `pre` tag that has global styles applied
with:

```
overflow-x: auto
```

I think the browser reserves space for the horizontal scrollbar (which
will never show up because the Message text is wrapping...) and that's
why the vertical one shows up.

Fix is to disallow horizontal overflowing, which will also remove the
unnecessary vertical scrollbar placeholder

before:
<img width="1085" height="114" alt="Screenshot 2025-10-09 at 15 09 34"
src="https://github.com/user-attachments/assets/41d2f5e2-d3ed-4b2e-9804-dd5d79b93d3e"
/>

after:
<img width="1069" height="110" alt="Screenshot 2025-10-09 at 15 09 27"
src="https://github.com/user-attachments/assets/67bd63d5-32f2-4eba-a4ee-402625aed7f0"
/>

Author: TkDodo

static/app/components/events/interfaces/message.tsx

@@ -75,5 +75,6 @@ const PlainPre = styled('pre')`
   border: 0;
   margin-bottom: 0;
   white-space: pre-wrap;
+  overflow-x: unset;
   word-break: break-all;
 `;