Remove self-hosted on matrix

[Kyle-Ye]

Also added macos-15 label to self-hosted runner so that it can be automatically be picked.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 24.88%. Comparing base (7c4f2b0) to head (e7458c3).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
.../Integration/PlatformHostingControllerHelper.swift	0.00%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #444      +/-   ##
==========================================
- Coverage   24.89%   24.88%   -0.01%     
==========================================
  Files         451      451              
  Lines       24951    24959       +8     
==========================================
  Hits         6211     6211              
- Misses      18740    18748       +8     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.