[DRE-maint] imagetooth is marked for autoremoval from testing

[Debian testing autoremoval watch]

imagetooth 2.0.1-1.1 is marked for autoremoval from testing on 2018-03-08

It (build-)depends on packages with these RC bugs:
888193: ruby-rmagick: FTBFS on ruby2.5: <FrozenError(<can't modify frozen Magick::Image>)>