fix: don't show unread badge if showing all

[iamacook]

What it solves

Resolves #1487

How this PR fixes it

The unread badge is hidden if showing all notifications (when there are more unread notifications than the notification limit).

How to test it

1. Queue >4 notifcations, without reading them.
2. Open the notification centre and observe an unread badge on the expand button.
3. Expand the list and no longer observe an unread badge.
4. Hiding again (without having read the later notifications) should display the unread badge again.

Screenshots

[github-actions]

Branch preview

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https://notification_badge--webcore.review-web-core.5afe.dev

[github-actions]

ESLint Summary View Full Report

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Type	Occurrences	Fixable
Errors	0	0
Warnings	0	0
Ignored	0	N/A

• Result: ✅ success
• Annotations: 0 total

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^{Report generated by eslint-plus-action}

[katspaugh]

Thanks, LGTM. In the future, please keep "good first issues" for external contributors.