fix(cache/unstable): fix flaky fibonacci test

[lionel-rowe]

Fixes this: https://github.com/denoland/std/actions/runs/10625661936/job/29455981411?pr=5626

 ERRORS 

memoize() is performant for expensive fibonacci function => ./cache/memoize_test.ts:65:6
error: AssertionError: Expected actual: "1724984137590" to be close to "1724984137573": delta "17" is greater than "10".
  throw new AssertionError(
        ^
    at assertAlmostEquals (file:///D:/a/std/std/assert/almost_equals.ts:51:9)
    at file:///D:/a/std/std/cache/memoize_test.ts:73:3

 FAILURES 

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.34%. Comparing base (d279c0a) to head (cf75348).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5872   +/-   ##
=======================================
  Coverage   96.34%   96.34%           
=======================================
  Files         479      479           
  Lines       38674    38674           
  Branches     5628     5627    -1     
=======================================
+ Hits        37259    37262    +3     
+ Misses       1371     1368    -3     
  Partials       44       44           

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[lionel-rowe]

Something weird going on here, attempt 1 at a fix was apparently timing out after a full 10 seconds (successful fix logged <=2ms to complete in each environment). Are functions like performance.now, Date.now etc now being globally overridden in CI or something?

https://github.com/denoland/std/actions/runs/10625999673/job/29456871384

[iuioiua]

LGTM. @kt3k, any idea what could've caused the weird behavior as mentioned in #5872 (comment)?

[kt3k]

I don't think we override performance.now or Date.now in CI.

FakeTime overrides Date class, but that shouldn't affect this test case (Test cases in a single file should be executed sequentially even with --parallel flag)

So I have no idea what caused the above error