Fix test_choi_to_kraus() randomly crashing

[renatomello]

Checklist:

• Reviewers confirm new code works as expected.
• Tests are passing.
• Coverage does not decrease.
• Documentation is updated.

[renatomello]

Since choi_to_kraus() depends on a spectral decomposition (or SVD), sometimes the numerical precision becomes 1-3% above qibo.config.PRECISION_TOL. Therefore, I increased precision for those tests and they should be fine now.

[codecov]

Codecov Report

Base: 100.00% // Head: 100.00% // No change to project coverage 👍

Coverage data is based on head (4bb7fb3) compared to base (96b47b3).
Patch coverage: 100.00% of modified lines in pull request are covered.

❗ Current head 4bb7fb3 differs from pull request most recent head 9d584fb. Consider uploading reports for the commit 9d584fb to get more accurate results

Additional details and impacted files

@@            Coverage Diff            @@
##            master      #797   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
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  Files           97        97           
  Lines        12894     12894           
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  Hits         12894     12894           

Flag	Coverage Δ
unittests	100.00% <100.00%> (ø)

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Impacted Files	Coverage Δ
...test_quantum_info_superoperator_transformations.py	100.00% <100.00%> (ø)

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[renatomello]

This is ready for merge after review @alecandido @andrea-pasquale

[alecandido]

Fine by me, but are you sure is it okay with increasing the tolerance by a factor of 10?

In particular, if raising tolerance is the chosen solution, a factor of 2 would have been sufficient.

[renatomello]

Fine by me, but are you sure is it okay with increasing the tolerance by a factor of 10?

In particular, if raising tolerance is the chosen solution, a factor of 2 would have been sufficient.

Changed it.

[andrea-pasquale]

Thanks @renatomello.