Check libidn2 version before proceding with one of the tests.

A known issue in libidn2 causes one of the tests of a fake A-label
to fail.  The problem should be corrected in version 2.0.5 of
libidn2.
7 jobs for 139-tests-for-idna2008-libidn2-merge-v9_11 in 8 minutes and 33 seconds (queued for 1 minute and 23 seconds)
Status Job ID Name Coverage
  Precheck
passed precheck:debian:sid:amd64 #6742
docker linux

00:00:11

 
  Build
passed build:debian:sid:amd64 #6743
docker linux

00:02:05

passed build:debian:sid:i386 #6745
docker linux

00:02:22

 
  Test
passed systemtest:debian:sid:amd64 #6750
docker linux

00:04:18

passed systemtest:debian:sid:i386 #6751
docker linux

00:04:27

passed unittest:debian:sid:amd64 #6747
docker linux

00:00:51

passed unittest:debian:sid:i386 #6749
docker linux

00:00:39