Add version 3.8.0 -> 3.9.0 to get_next_version() function

openvidu-deployment/update.sh

@@ -45,6 +45,7 @@ get_next_version() {
     "3.6.0") echo "3.6.1" ;;
     "3.6.1") echo "3.7.0" ;;
     "3.7.0") echo "3.8.0" ;;
+    "3.8.0") echo "3.9.0" ;;
     *) echo "" ;;
   esac
 }