fix(vis-network): unit tests

[ErwanRaulo]

Adapt unit tests and fixture to current implementation of dataset.

i need advice on unknown license computation, i removed their test because current algorithm does handle this case, for example :

• "license": "a string licence (should be unknown)"
• will not give {unknown: 1}
• because computeLicense fn expects an iterable and a string is an iterable so the number of licenses will be the number of characters.

does unknown license is buggy or not handled anymore ?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 59.15%. Comparing base (28ee6a9) to head (caaf1b9).
Report is 211 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##            master     #528       +/-   ##
============================================
- Coverage   100.00%   59.15%   -40.85%     
============================================
  Files           15       38       +23     
  Lines          649     2921     +2272     
  Branches         0       14       +14     
============================================
+ Hits           649     1728     +1079     
- Misses           0     1193     +1193     

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