Fix `WmdSimilarity` documentation (#2217)
Fix `WmdSimilarity` documentation (#2217)

* Update documentation for WmdSimilarity.

* Fix curly braces issue.

* Fix WmdSimilarity docstring example.

RaRe-Technologies/gensim,RaRe-Technologies/gensim,gojomo/gensim,gojomo/gensim,piskvorky/gensim,RaRe-Technologies/gensim,gojomo/gensim,piskvorky/gensim,gojomo/gensim,RaRe-Technologies/gensim,piskvorky/gensim