fix(filtering): Do not show filter unread mentions button while filtering

[max65482]

☑️ Resolves

• Fix Remove redundant unread mention button when filtering for unread mentions #16473

🖌️ UI Checklist

🖼️ Screenshots / Screencasts

🏚️ Before	🏡 After

🚧 Tasks

• ...

🏁 Checklist

• 🌏 Tested with different browsers / clients:
  • Chromium (Chrome / Edge / Opera / Brave)
  • Firefox
  • Safari
  • Talk Desktop
  • Integrations with Files sidebar and other apps
  • Not risky to browser differences / client
• 🖌️ Design was reviewed, approved or inspired by the design team
• ⛑️ Tests are included or not possible
• 📗 User documentation in https://github.com/nextcloud/documentation/tree/master/user_manual/talk has been updated or is not required

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[nickvergessen]

It would still make sense when we are filtering by conversation names or for meeting conversations or unread messages in general?

[Antreesy]

Yeah, I'd say original issue is unclear about this. Button should not be shown, only if there are unread conversations out of screen, not when filtering