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 in 6 minutes and 47 seconds (queued for 43 seconds)
Status Job ID Name Coverage
  Precheck
passed #6717
linux docker
precheck:debian:sid:amd64

00:00:13

 
  Build
passed #6718
linux docker
build:debian:sid:amd64

00:01:33

passed #6719
linux docker
build:debian:sid:i386

00:01:34

 
  Test
passed #6722
linux docker
systemtest:debian:sid:amd64

00:04:58

passed #6723
linux docker
systemtest:debian:sid:i386

00:04:57

passed #6720
linux docker
unittest:debian:sid:amd64

00:01:05

passed #6721
linux docker
unittest:debian:sid:i386

00:00:57