The composer.json incorrectly claims that this release is still compatible with Drupal 8.7 and running composer update will try to update that. Either update to Drupal 8.8 or require an earlier version until you can do so:
composer require drupal/token:1.6
Contributors (8)
Chris Burge, Berdir, Matroskeen, Sergiu Stici, thalles, maximpodorov, idebr, czigor