🩹 fix MQT Core update workflow

[burgholzer]

Description

This PR fixes the MQT Core update workflow. If successful, the corresponding CI run in this PR should trigger an update to MQT Core 2.6.0

Checklist:

• [x] The pull request only contains commits that are related to it.
• [x] I have added appropriate tests and documentation.
• [x] I have made sure that all CI jobs on GitHub pass.
• [x] The pull request introduces no new warnings and follows the project's style guidelines.