Do not log to stdout in tests

[tvdeyen]

Summary

Due to a change in #6244 we now log to stdout in tests, instead of to the test.log file. This clutters test output on CircleCI

https://app.circleci.com/pipelines/github/solidusio/solidus/8111/workflows/1ccfe0fe-1905-4145-9d50-8af1c93f258b/jobs/80080/parallel-runs/0/steps/0-112

Instead we just let Rails / RSpec do their default logging.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.82%. Comparing base (cfb5acb) to head (abcf431).
Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6268      +/-   ##
==========================================
- Coverage   88.82%   88.82%   -0.01%     
==========================================
  Files         851      851              
  Lines       18349    18348       -1     
==========================================
- Hits        16299    16298       -1     
  Misses       2050     2050              

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[mamhoff]

Thanks for this find!