The highlight box is out of the tutorial box on Firefox

[Helen09]

Repro steps:

1. Navigate to https://makecode.adafruit.com/beta#editor
2. Click "More..." -> "High Contrast On" to open high contrast
3. Click "HOME" to back to home page and scroll down to click tutorials one by one

Expected result:(Edge, Chrome & IE)

Actual result(Firefox): The highlight box is out of the tutorial box on Firefox