gazebo is marked for autoremoval from testing

[Debian testing autoremoval watch]

gazebo 9.0.0+dfsg5-4.1 is marked for autoremoval from testing on 2018-08-19

It (build-)depends on packages with these RC bugs:
888350: blender: FTBFS with FFmpeg 4.0
897713: blender: ftbfs with GCC-8
897756: insighttoolkit4: fw4spl: ftbfs with GCC-8
897775: insighttoolkit4: itksnap: ftbfs with GCC-8