Fix format security error in rgbdx_sync.cpp

[sloretz]

This fixes a regression in Noetic. All the rtabmap_ros binary jobs in Noetic are failing with the following error:

18:59:28 /opt/ros/noetic/include/ros/console.h:351:176: error: format not a string literal and no format arguments [-Werror=format-security]
...
18:59:28 /tmp/binarydeb/ros-noetic-rtabmap-sync-0.21.3/src/nodelets/rgbdx_sync.cpp:167:3: note: in expansion of macro ‘NODELET_INFO’
18:59:28   167 |   NODELET_INFO(subscribedTopicsMsg.c_str());
18:59:28       |   ^~~~~~~~~~~~

https://build.ros.org/job/Nbin_uF64__rtabmap_sync__ubuntu_focal_amd64__binary/6

Note I edited this in the github UI. I haven't built this locally.

[matlabbe]

Thx, I'll start a new release