[TASK] Replace abandoned IDNA converter

The package "phpwhois/idna-convert" was abandoned in favor of
the package "mso/idna-convert".

Change-Id: Ie5bb7be899b6810d825a019b62cbc326521f8018
Resolves: #72548
Releases: master, 7.6
Reviewed-on: https://review.typo3.org/45632


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>