RT_PLUGINS=/usr/bin/rtorrent/var/www/ui/rtorrent/plugins
# list all plugins
ls -la $RT_PLUGINS
# list all not used plugins
ls -la ${RT_PLUGINS}.notused
# remove or safety move to other directory...
# remove...
rm -rf $RT_PLUGINS/filemanager
# safety move
mv -f $RT_PLUGINS/filemanager ${RT_PLUGINS}.notused/