text: Title: Fix deprecations in SoftCosineSimilarity
  Body: When running our CI test suite, I see an array of deprecation warnings:
  
  https://dev.azure.com/rare-technologies/gensim-ci/_build/results?buildId=287&view=logs&jobId=f9575ddc-dec8-54e6-9d26-abb8bdd9bed7&j=f9575ddc-dec8-54e6-9d26-abb8bdd9bed7&t=180156a9-2bf9-537d-c84a-ef9e808c0367
  
  Some are from gensim, some from scipy:
  <img width="1440" alt="Screen Shot 2020-09-09 at 09 16 00" src="https://user-images.githubusercontent.com/610412/92567026-635b8f00-f27d-11ea-9d5f-c56f3ba7c08b.png">
  
  @Witiko could you please have a look? Is it something your existing PR already addresses?
  
  If not, can you please fix those? Thanks.