Fix format specifier

[garaemon]

• Use %u instead of %lu to print Ogre::Texture::getWidth() and
  Ogre::Texture::getHeight() because they return uint32.

https://www.ogre3d.org/docs/api/1.9/class_ogre_1_1_texture.html#a03b77fa04181bc3bd30323555b425667

The following warning will disappear after merging this PR.

/home/ryohei/gitai/catkin_ws/src/jsk_visualization/jsk_rviz_plugins/src/camera_info_display.cpp: In member function ‘virtual void jsk_rviz_plugins::CameraInfoDisplay::drawImageTexture()’:
/home/ryohei/gitai/catkin_ws/src/jsk_visualization/jsk_rviz_plugins/src/camera_info_display.cpp:369:1173: warning: format ‘%lu’ expects argument of type ‘long unsigned int’, but argument 8 has type ‘Ogre::uint32 {aka unsigned int}’ [-Wformat=]
/home/ryohei/gitai/catkin_ws/src/jsk_visualization/jsk_rviz_plugins/src/camera_info_display.cpp:370:1171: warning: format ‘%lu’ expects argument of type ‘long unsigned int’, but argument 8 has type ‘Ogre::uint32 {aka unsigned int}’ [-Wformat=]