Revert "feat: make seisbench dependency optional (#578)"

[JiaoMaWHU]

This reverts commit a4ced3a.

This commit failed python package build post merging due to

=========================== short test summary info ============================
ERROR python/tests/algorithms/ml/test_arrival.py - requests.exceptions.SSLError: HTTPSConnectionPool(host='hifis-storage.desy.de', port=2880): Max retries exceeded with url: /Helmholtz/HelmholtzAI/SeisBench/models/v3/phasenet (Caused by SSLError(SSLCertVerificationError(1, '[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1131)')))
!!!!!!!!!!!!!!!!!!!! Interrupted: 1 error during collection !!!!!!!!!!!!!!!!!!!!
============================== 1 error in 14.03s ===============================