Comment out non-existent html_static_path in doc

[sbraz]

Fixes WARNING: html_static_path entry 'docs/_static' does not exist

[sbraz]

No need to make a new release for that, it's just something I noticed while building the new version's doc :)

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@248fe63). Click here to learn what that means.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             master    #41   +/-   ##
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  Coverage          ?   100%           
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  Files             ?      1           
  Lines             ?     83           
  Branches          ?     16           
=======================================
  Hits              ?     83           
  Misses            ?      0           
  Partials          ?      0

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[briancurtin]

Thanks!