Fix normal text shortcut in rich text editor

Changelog: fixed

What does this MR do and why?

The rich text editor has loads of helpful shortcuts for formatting https://docs.gitlab.com/ee/user/shortcuts.html#formatting

This MR fixes apply normal text style which was not working.

Command + Alt + 0

Control + Alt + 0

Apply normal text style

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Before	After
Kapture 2024-05-01 at 13.01.15.mp4	Kapture 2024-05-01 at 13.02.14.mp4

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Use the rich text editor, for example in an issue comment
2. Write some text and apply a heading style
3. Use the apply normal text style keyboard shortcut; macOS: Command + Alt + 0 ; Windows: Control + Alt + 0;
4. Magic ✨