fix flaky rl test

[jesterhazy]

Description of changes:

fix flaky fl test

Merge Checklist

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• I have added tests that prove my fix is effective or that my feature works (if appropriate)
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[codecov-io]

Codecov Report

Merging #535 into master will decrease coverage by 0.11%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #535      +/-   ##
==========================================
- Coverage   92.83%   92.71%   -0.12%     
==========================================
  Files          71       71              
  Lines        5343     5343              
==========================================
- Hits         4960     4954       -6     
- Misses        383      389       +6

Impacted Files	Coverage Δ
src/sagemaker/local/image.py	87.76% <0%> (-1.84%)	⬇️

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