Describe the bug
I wasn't able to reach all characters.

Steps to Reproduce

1. Open characters dialog.
2. Set screen resolution so that dialog is cut
3. Unable to scroll all the characters.

Expected behavior
Able to reach all characters.

Screenshots

Environment information

• Device: MacBook
• OS: MacOS 10.14.5
• Browser and version: Chrome 76.0.3809.100
• Plugins and version: master and 6.3 Gutenberg
• Theme and version: Theme scaffold
• Other installed plugin(s) and version(s):