remove the setup.py clean step from builddocs.sh

Author: tazend

scripts/builddocs.sh

@@ -17,7 +17,6 @@ done
 
 shift $((OPTIND-1))
 
-python setup.py clean
 pip install -r doc_requirements.txt
 scripts/build.sh -j${OPT_JOBS} -d
 mkdocs build