Properly remove forbidden species from edge

[mjohnson541]

This fixes a bug that occurs when forbidden species are removed from the edge. Currently this is done manually not using removeSpeciesFromEdge which leaves the species and reactions still in memory in more obscure locations leading to key errors later on. This PR switches to using removeSpeciesFromEdge avoiding these problems.

[codecov]

Codecov Report

Merging #1556 into master will increase coverage by <.01%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master    #1556      +/-   ##
==========================================
+ Coverage   41.85%   41.86%   +<.01%     
==========================================
  Files         165      165              
  Lines       28014    28008       -6     
  Branches     5716     5713       -3     
==========================================
  Hits        11726    11726              
+ Misses      15500    15494       -6     
  Partials      788      788

Impacted Files	Coverage Δ
rmgpy/rmg/model.py	39.94% <0%> (+0.21%)	⬆️

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