force removal of docs' dir since it might not exist yet

Author: lukaszstolarczuk

utils/docker/run-doc-update.sh

@@ -48,7 +48,7 @@ git checkout -B $GH_PAGES_NAME upstream/gh-pages
 git clean -dfx
 
 # Clean old content, since some files might have been deleted
-rm -r ./$VERSION
+rm -rf ./$VERSION
 mkdir -p ./$VERSION/doxygen/
 
 cp -r ../cpp_html/* ./$VERSION/doxygen/