KeyboardShortcuts: Update delete shortcut to use Shift + Delete and add Backspace alias

[yogeshbhutkar]

Fixes: #68139

What, Why & How?

Previously, the shortcut to remove the selected blocks was Control Option Z on Mac, or Control Alt Z on Windows.

This PR introduces the usage of Shift + Delete for performing the same.

Testing Instructions

1. Create a block.
2. Press the key combination Shift + Delete and observe the removal of the block.

Screencast

Screenshot

[github-actions]

Warning: Type of PR label mismatch

To merge this PR, it requires exactly 1 label indicating the type of PR. Other labels are optional and not being checked here.

• Type-related labels to choose from: [Type] Automated Testing, [Type] Breaking Change, [Type] Bug, [Type] Build Tooling, [Type] Code Quality, [Type] Copy, [Type] Developer Documentation, [Type] Enhancement, [Type] Experimental, [Type] Feature, [Type] New API, [Type] Task, [Type] Technical Prototype, [Type] Performance, [Type] Project Management, [Type] Regression, [Type] Security, [Type] WP Core Ticket, Backport from WordPress Core, Gutenberg Plugin.
• Labels found: .

Read more about Type labels in Gutenberg. Don't worry if you don't have the required permissions to add labels; the PR reviewer should be able to help with the task.

[github-actions]

The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

If you're merging code through a pull request on GitHub, copy and paste the following into the bottom of the merge commit message.

Co-authored-by: yogeshbhutkar <[email protected]>
Co-authored-by: jarekmorawski <[email protected]>
Co-authored-by: Mamaduka <[email protected]>
Co-authored-by: t-hamano <[email protected]>
Co-authored-by: jasmussen <[email protected]>

To understand the WordPress project's expectations around crediting contributors, please review the Contributor Attribution page in the Core Handbook.

[yogeshbhutkar]

Looks like some Playwright tests are failing, will be adding a commit to fix the failing test cases.