qt3d-opensource-src is marked for autoremoval from testing

[Debian testing autoremoval watch]

qt3d-opensource-src 5.7.1+dfsg-2 is marked for autoremoval from testing on 
2017-07-27

It (build-)depends on packages with these RC bugs:
864729: assimp: Bundles ConvertUTF code which is under non-DFSG license