chore: Fix flaky unit test

[gmlewis]

This fixes the flaky unit test demonstrated here:
https://github.com/google/go-github/actions/runs/28966637656/job/85951381658

 --- FAIL: TestDo_rateLimit_abortSleepContextCancelled (0.05s)
github_test.go:2873: Expected 1 requests, got 0
FAIL

[gmlewis]

cc: @stevehipwell - @alexandear - @Not-Dhananjay-Mishra

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.51%. Comparing base (da81e17) to head (b4f4800).

Additional details and impacted files

@@ Coverage Diff @@## master #4374 +/- ##
=======================================
Coverage 97.51% 97.51% =======================================
Files 193 193 Lines 19526 19526 =======================================
Hits 19040 19040 + Misses 269 268 -1 - Partials 217 218 +1 

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[stevehipwell]

LGTM