Add tests for check_cv method with and without random_state

[thibaultcordier]

Description

The modification proposes to resolve the bug by imposing a default value for random_state in check_cv method tests, so that the method retains split behavior even if random_state is set to None.

Fixes #336

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• Test if check_cv retains split behavior if random_state is set to None.
• Test if check_cv retains split behavior if random_state is set a certain value.

Checklist

• I have read the contributing guidelines
• I have updated the HISTORY.rst and AUTHORS.rst files
• Linting passes successfully : make lint
• Typing passes successfully : make type-check
• Unit tests pass successfully : make tests
• Coverage is 100% : make coverage
• Documentation builds successfully : make doc

[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (0331c98) 100.00% compared to head (73b223a) 100.00%.
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##            master      #337   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           39        39           
  Lines         4278      4303   +25     
  Branches       467       474    +7     
=========================================
+ Hits          4278      4303   +25     

Files Changed	Coverage Δ
mapie/tests/test_utils.py	100.00% <100.00%> (ø)
mapie/utils.py	100.00% <100.00%> (ø)

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[LacombeLouis]

I think this fixes the problem. I just think some small details need to be added.