fix: hide mark all as read button with no uread notifications

[matteoscurati]

Description

This PR introduces a small fix to hide the "Mark all as read" button for notifications when all notifications are already read.

Related issues

Fixes:

Manual testing steps

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Screenshots/Recordings

Before

After

Pre-merge author checklist

• I've followed MetaMask Contributor Docs and MetaMask Extension Coding Standards.
• I've completed the PR template to the best of my ability
• I’ve included tests if applicable
• I’ve documented my code using JSDoc format if applicable
• I’ve applied the right labels on the PR (see labeling guidelines). Not required for external contributors.

Pre-merge reviewer checklist

• I've manually tested the PR (e.g. pull and build branch, run the app, test code being changed).
• I confirm that this PR addresses all acceptance criteria described in the ticket it closes and includes the necessary testing evidence such as recordings and or screenshots.

[github-actions]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 65.38%. Comparing base (85783b1) to head (f2f17b5).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop   #25348   +/-   ##
========================================
  Coverage    65.38%   65.38%           
========================================
  Files         1382     1382           
  Lines        54765    54767    +2     
  Branches     14367    14368    +1     
========================================
+ Hits         35807    35809    +2     
  Misses       18958    18958           

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