Scheduler tasks cannot be created with EXT:ter installed

What was the cause of the issue?

EXT:ter still uses an outdated interface (tx_scheduler_AdditionalFieldProvider) in the file class.tx_ter_updateExtensionIndexTask_additionalFieldProvider.php. This leads to an error message when trying to create a scheduler task

Steps to reproduce

Go to the scheduler BE module, try to create a new task.

Output of error log

( ! ) Fatal error: Interface 'tx_scheduler_AdditionalFieldProvider' not found in /var/www/html/typo3conf/ext/ter/task/class.tx_ter_updateExtensionIndexTask_additionalFieldProvider.php on line 25