Fix f1 score for macro and ignore index

[SkafteNicki]

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• Did you make sure to update the docs?
• Did you write any new necessary tests?

What does this PR do?

Fixes #486

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[codecov]

Codecov Report

Merging #495 (f3255b4) into master (fd58980) will increase coverage by 0%.
The diff coverage is 100%.

@@          Coverage Diff          @@
##           master   #495   +/-   ##
=====================================
  Coverage      95%    95%           
=====================================
  Files         130    130           
  Lines        4586   4586           
=====================================
+ Hits         4363   4373   +10     
+ Misses        223    213   -10     

[Borda]

don't we have a test for this seems it can be broken anytime in future the same way...

[SkafteNicki]

@Borda have added test now. But we did not have test because its a corner case.