Type error prevents SV filtration

[holtgrewe]

Describe the bug
When writing out the VCF for the SV filtration in the worker, VarFish may write out floats for integer FORMAT fields. This leads to an error in parsing with recent noodles-vcf versions.

To Reproduce
See row ending in

GT:cn:GQ        1/1:0.03:17

The corresponding header line is

##FORMAT=<ID=cn,Number=1,Type=Integer,Description="Copy number of the variant in the sample">

Expected behavior
Coerce value to int.

Additional context
N/A