Docs: Remove list of keyboard shortcuts from FAQ page

[t-hamano]

Closes #60627

What?

This PR completely removes the shortcut list from the FAQ documentation page.

Why?

The current shortcut list is manually maintained, so updates to this page may be overlooked and may become out of date in the future. In order to provide a complete and accurate list, it should be sufficient to include the means to access the shortcut modal.

How?

Since the method to access the shortcut modal was already described, I simply deleted only the shortcut list.

Testing Instructions

Check out the shortcuts section of the new FAQ page:

https://github.com/WordPress/gutenberg/blob/docs/remove-faq-shortcut-list/docs/getting-started/faq.md#are-there-keyboard-shortcuts-for-gutenberg

[github-actions]

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Co-authored-by: t-hamano <wildworks@git.wordpress.org>
Co-authored-by: juanmaguitar <juanmaguitar@git.wordpress.org>
Co-authored-by: afercia <afercia@git.wordpress.org>

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[juanmaguitar]

LGTM 👍