fix: unread message clearing on convo change

[tlebon]

Description

Noticed an issue where unread messages would be cleared when changing conversations and going back to the original convo.
Appears to be a regression introduced in #17158

Screenshots/Screencast (for UI changes)

Before:
https://github.com/wireapp/wire-webapp/assets/37285713/65fb81b5-93d7-4222-8b96-f63004aba8c2

After:
https://github.com/wireapp/wire-webapp/assets/37285713/772f3419-4049-474a-a0cb-f3228eefb053

Checklist

• PR has been self reviewed by the author;
• Hard-to-understand areas of the code have been commented;
• If it is a core feature, unit tests have been added;

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 46.07%. Comparing base (3c78c48) to head (ea7eb83).
Report is 4 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev   #17380      +/-   ##
==========================================
+ Coverage   46.05%   46.07%   +0.01%     
==========================================
  Files         753      753              
  Lines       24736    24737       +1     
  Branches     5669     5669              
==========================================
+ Hits        11392    11397       +5     
+ Misses      11913    11910       -3     
+ Partials     1431     1430       -1     

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud

[PatrykBuniX]

Looks good