Switch the ElementCall UI test to call.element.io for stability

[stefanceriu]

Following testing failures here https://github.com/element-hq/element-x-ios/actions/runs/13125453338 and hgere https://github.com/element-hq/element-x-ios/actions/runs/13113051382

[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]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.57%. Comparing base (5d785b3) to head (f486b87).
Report is 1 commits behind head on develop.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3733      +/-   ##
===========================================
+ Coverage    77.56%   77.57%   +0.01%     
===========================================
  Files          797      797              
  Lines        69333    69333              
===========================================
+ Hits         53777    53786       +9     
+ Misses       15556    15547       -9     

Flag	Coverage Δ
unittests	70.33% <ø> (-0.02%)	⬇️

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[pixlwave]

lgtm