Address scroll bar styling

## Description

What is this white bar to the right of the Data section of the Plot tab? Scrollbar to be - oh it seems like it is. It also appear on the gallery column, but only when there are enough cells for scrolling instead of just being there ahead of time. The scroll bar overlap the gallery area and touch the thumbnails a bit

## Expected Behavior

_What did you expect to happen instead?_

## Reproduction

## Environment

_Any additional information about your environment. E.g. OS version, python version, browser etc._