Merge pull request #159 from basf/dependabot/pip/docs/lxml-html-clean-0.4.0

Bump lxml-html-clean from 0.1.1 to 0.4.0 in /docs

Author: AnFreTh

docs/requirements_docs.txt

@@ -11,5 +11,5 @@ sphinx-book-theme==1.1.2
 pandoc==2.3
 sphinx-rtd-theme==2.0.0
 readthedocs-sphinx-ext==2.2.5
-lxml-html-clean==0.1.1
+lxml-html-clean==0.4.0
 pydata-sphinx-theme==0.15.2