add comment on /uppgrade_caldavzap.sh script

uppgrade_caldavzap.sh

     rm -r tracim/tracim/public/caldavzap
 fi
 
+# Update the code
 git clone https://github.com/algoo/caldavzap.git tracim/tracim/public/caldavzap
 rm -rf tracim/tracim/public/caldavzap/.git