[FIX] Nomogram: Fix crash on Python 3.8

[lanzagar]

Issue

On py3.8 nomogram crashed for logistic regression models with:
TypeError: only integer scalar arrays can be converted to a scalar index

Description of changes

Iterate over actual coefficient values (numbers) instead of rows of a ndarray (which are still ndarrays) to get a proper boolean value for reverse.

Includes

• Code changes
• Tests
• Documentation

[codecov]

Codecov Report

Merging #4591 into master will decrease coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #4591      +/-   ##
==========================================
- Coverage   83.61%   83.58%   -0.03%     
==========================================
  Files         281      276       -5     
  Lines       56189    55384     -805     
==========================================
- Hits        46982    46295     -687     
+ Misses       9207     9089     -118     

[PrimozGodec]

Thank you. It works fine now.