Bug: Live preview scrolls back to the top after editing the note

Hi,

I noticed a little bug in Markdown's live preview:

* Open a long note and edit something;
* Change to the live preview and scroll the page;
* Simplenote will bounce back to the top the first time you scroll. After that, scrolling works as intended.

It repeats every time you make an edit in the note and activate live preview.

I'm using Simplenote 2.13 on macOS 11.4.

A vide:

https://user-images.githubusercontent.com/19216581/123555483-52bccc80-d75c-11eb-88d7-8072894b92c3.mp4

Reproduce the reported sequence with a long Markdown note: edit it, activate live preview, and scroll. Done means the preview preserves the current scroll position on the first scroll after each edit, without the bounce to the top.

Written by the indexing model from the issue text.