Bump joblib from 0.17.0 to 1.2.0 in /docs (#207)

Bumps [joblib](https://github.com/joblib/joblib) from 0.17.0 to 1.2.0.
- [Release notes](https://github.com/joblib/joblib/releases)
- [Changelog](https://github.com/joblib/joblib/blob/master/CHANGES.rst)
- [Commits](https://github.com/joblib/joblib/compare/0.17.0...1.2.0)

---
updated-dependencies:
- dependency-name: joblib
  dependency-type: direct:production
...

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Signed-off-by: dependabot[bot] <support@github.com>
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docs/requirements.txt

@@ -1,7 +1,7 @@
 click==7.1.2
 future==0.18.2
 Jinja2==2.11.3
-joblib==0.17.0
+joblib==1.2.0
 livereload==2.6.3
 lunr==0.5.8
 Markdown==3.3