chore: loose test_interval_task_performance a bit to prevent flaky behaviour in CI

[danfimov]

Test usually breaks on random MRs: https://github.com/taskiq-python/taskiq/actions/runs/35246610124/job/105288375709?pr=661

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.37%. Comparing base (8a1b04d) to head (3107ec6).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #680   +/-   ##
=======================================
  Coverage   85.37%   85.37%           
=======================================
  Files          68       68           
  Lines        2660     2660           
=======================================
  Hits         2271     2271           
  Misses        389      389           

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