Change port in cancellation token test to reduce flakiness

[DenisBiryukov91]

Change port in cancellation token test to reduce flakiness

---

🏷️ Label-Based Checklist

Based on the labels applied to this PR, please complete these additional requirements:

Labels: internal

🏠 Internal Change

This PR is marked as internal (not user-facing):

• No API changes - Public APIs unchanged
• No behavior changes - External behavior identical
• Refactoring/maintenance - Code improvements only
• Tests still pass - All existing tests pass without modification

Lighter review: Internal changes may have lighter review requirements.

Instructions:

1. Check off items as you complete them (change - [ ] to - [x])
2. The PR checklist CI will verify these are completed

This checklist updates automatically when labels change, but preserves your checked boxes.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 71.82%. Comparing base (ffad527) to head (f254875).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2356      +/-   ##
==========================================
- Coverage   72.76%   71.82%   -0.95%     
==========================================
  Files         387      387              
  Lines       61972    61966       -6     
==========================================
- Hits        45097    44504     -593     
- Misses      16875    17462     +587     

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