Update Packages for 6.8.1

[aaronjorbin]

This includes the following changes:

• [WP6.8.1] ToggleGroupControl: Fix active background for empty string value gutenberg#70000
• [WP6.8.1] Keyboard Shortcuts: Revert delete shortcut to access + z gutenberg#69998
• [WP6.8.1] Author, Author Name block: fix PHP warning error when there is no context gutenberg#70001
• [WP6.8] Fix 'wp-polyfill' script dependents unit test gutenberg#70006
• Use split view for meta boxes only when canvas is iframed and “Desktop” view gutenberg#69958

Trac ticket:

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[github-actions]

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[t-hamano]

Since 6.8.1 has already been released, can this PR be closed?