For #21037 - Add a delete history menu item

[gabrielluong]

This removes the existing "Delete history" button in the History in favour of a menu item

Fixes #21037

Pull Request checklist

• Tests: This PR includes thorough tests or an explanation of why it does not
• Screenshots: This PR includes screenshots or GIFs of the changes made or an explanation of why it does not
• Accessibility: The code in this PR follows accessibility best practices or does not include any user facing features. In addition, it includes a screenshot of a successful accessibility scan to ensure no new defects are added to the product.

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[MozillaNoah]

Looks good to me