Install lxml_html_clean dependency

Author: Senui

.github/workflows/website-ci.yml

@@ -74,7 +74,7 @@ jobs:
         eval "$(pyenv init --path)"
         eval "$(pyenv init -)"
         pyenv shell 3.9.1
-        pip install lxml
+        pip install lxml_html_clean
         cmake \
           -Dwebsite=on \
           -Dtest=off \