feat: update group avatar [WPB-15794]

[e-maad]

WPB-15794 [Web] Adjust group avatars (not channels) to be in line with channel mocks

Description

Updated group avatar.
Design reference: https://www.figma.com/design/jnygr7PEOk1yHgjBF18udc/Desktop?node-id=6170-7172&t=1qua0jvbIGLcDwG1-0

Screenshots/Screencast (for UI changes)

Old:

New:

Checklist

• mentions the JIRA issue in the PR name (Ex. [WPB-XXXX])
• 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;

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 33.33333% with 2 lines in your changes missing coverage. Please review.

Project coverage is 45.72%. Comparing base (328b309) to head (e250f83).
Report is 5 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev   #18719      +/-   ##
==========================================
- Coverage   45.74%   45.72%   -0.02%     
==========================================
  Files         944      944              
  Lines       27876    27874       -2     
  Branches     6292     6292              
==========================================
- Hits        12751    12746       -5     
- Misses      13534    13537       +3     
  Partials     1591     1591