Scrollbar thumb changes length when scolling

### Checked for duplicates?

- [x] This issue is not a duplicate

### Does it also happen in the desktop version?

- [x] This bug does not occur in the latest version of Anki Desktop

### What are the steps to reproduce this bug?

Have tags/card that take up different numbers of lines then scroll. It's best to see the bug in action:

https://github.com/user-attachments/assets/87e8eca3-fcb7-4fac-9716-662173ce9a3e

### Expected behaviour

The length of the scrollbar "thumb" should not change while scrolling.

### Debug info

```text
AnkiDroid Version = 2.23.0alpha8 (f9e524a31c98e4f5d922f7b2c5217efe4d350009)
Backend Version = 0.1.62-anki25.09.2 (25.09.2 3890e12c9e48c028c3f12aa58cb64bd9f8895e30)
Android Version = 13 (SDK 33)
ProductFlavor = full
Device Info = Xiaomi | POCO | mondrian | mondrian_global | 23013PC75G | qcom
Webview User Agent = Mozilla/5.0 (Linux; Android 13; 23013PC75G Build/TKQ1.220905.001; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/141.0.7390.122 Mobile Safari/537.36
ACRA UUID = 4afc3b3f-e93f-4a66-bc71-2b9476ef9eb0
FSRS = 5.1.0 (Enabled: true)
Crash Reports Enabled = true
```

### (Optional) Anything else you want to share?

Anki Desktop limits all cards in the browser/tags to take only one row, which seems to eliminate the issue.

### Research

- [x] I have checked the [manual](https://ankidroid.org/docs/manual.html) and the [FAQ](https://github.com/ankidroid/Anki-Android/wiki/FAQ) and could not find a solution to my issue
- [x] (Optional) I have confirmed the issue is not resolved in the latest alpha release ([instructions](https://docs.ankidroid.org/manual.html#betaTesting))