Set tests stderr output tracing level to OFF

[mario-nt]

Fixes #1069

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 76.45%. Comparing base (b827c31) to head (01c1041).

Files with missing lines	Patch %	Lines
src/bootstrap/logging.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1094   +/-   ##
========================================
  Coverage    76.44%   76.45%           
========================================
  Files          174      174           
  Lines        11488    11488           
  Branches     11488    11488           
========================================
+ Hits          8782     8783    +1     
  Misses        2507     2507           
+ Partials       199      198    -1     

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