Fix unstable test

[martintmk]

Details on the issue fix or feature implementation

I noticed this test failing so I made it more deterministic. Should not happen anymore.

Contributes to #1362

Confirm the following

• I started this PR by branching from the head of the default branch
• I have targeted the PR to merge into the default branch
• I have included unit tests for the issue/feature
• I have successfully run a local build

[codecov]

Codecov Report

Merging #1396 (f87f6ff) into main (cebe145) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1396   +/-   ##
=======================================
  Coverage   83.79%   83.79%           
=======================================
  Files         273      273           
  Lines        6475     6475           
  Branches     1010     1010           
=======================================
  Hits         5426     5426           
  Misses        840      840           
  Partials      209      209           

Flag	Coverage Δ
linux	?
macos	83.79% <ø> (ø)
windows	?

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Impacted Files	Coverage Δ
src/Polly.Core/Retry/RetryResilienceStrategy.cs	100.00% <ø> (ø)