text: Title: Update WMD documentation
  Body: A user reported a documentation issue on the mailing list: https://groups.google.com/g/gensim/c/8nobtm9tu-g.
  
  The report shows two problems:
  
  1) Something changed with `wmdistance` between 3.8 and 4.0 that is not properly captured in the [Migration notes](https://github.com/RaRe-Technologies/gensim/wiki/Migrating-from-Gensim-3.x-to-4).
  
  2. The [WMD tutorial](https://radimrehurek.com/gensim_4.0.0/auto_examples/tutorials/run_wmd.html#normalizing-word2vec-vectors) contains instructions that are now outdated in 4.0: 
  
     > When using the wmdistance method, it is beneficial to normalize the word2vec vectors first, so they all have equal length. To do this, simply call model.init_sims(replace=True) and Gensim will take care of that for you.
  
     …And then our own tutorial logs a `WARNING : destructive init_sims(replace=True) deprecated & no longer required for space-efficiency`, which looks silly.