Bug#1035458: libtorch-dev: broken symlinks: /usr/lib/x86_64-linux-gnu/libcaffe2_*.so -> libcaffe2_*.so.1.13

[M. Zhou]

Control: severity -1 important
Control: fixed -1 1.13.1+dfsg-5

I believe these symlinks were deprecated already. These symlinks are removed in 
1.13.1+dfsg-5 (experimental).
I'm not able to prepare a 1.13.1+dfsg-4.1 release to only remove these symlinks 
within a short time... too busy lately.
So just downgrading the severity as it is not expected to harm any 
functionality.