Migrate v2 glossary API to v3

Problem/Motivation

DeepL released the v3 endpoint for its glossary functionality. Besides supporting multilingual glossaries (which we won't use) it als supports editing of exisitng glossaries.
Further information can be found here: https://github.com/DeepLcom/deepl-php?tab=readme-ov-file#glossaries

Proposed resolution

• follow the migration guide and rewrite the exisiting DeeplGlossaryApi methods
• update existing phpunit tests