Bug#654839: retitle this to bring it up to date

[Gert Wollny]

Control: retitle -1 Paraview should use system VTK libraries

Unfortunately, upstream comented on this that it would be difficult to
use a seperate version of VTK because their development process just
doesn't take care of this. See, e.g. this recent thread:  

https://lists.debian.org/debian-science/2018/03/msg00048.html

Therefore, I keep that at severity wishlist. 

best, 
Gert