Fix pendulum version in tests

[medvedev1088]

What?

Fix pendulum version in tests

Why?

Prevents an error in tests https://github.com/blockchain-etl/ethereum-etl-airflow/actions/runs/8027295703/job/21932297315

==================================== ERRORS ====================================
________________ ERROR collecting tests/test_dag_validation.py _________________
tests/test_dag_validation.py:4: in <module>
    from airflow.models import DagBag, Variable
/opt/hostedtoolcache/Python/3.8.12/x64/lib/python3.8/site-packages/airflow/__init__.py:42: in <module>
    from airflow import settings
/opt/hostedtoolcache/Python/3.8.12/x64/lib/python3.8/site-packages/airflow/settings.py:49: in <module>
    TIMEZONE = pendulum.tz.timezone("UTC")
E   TypeError: 'module' object is not callable
=========================== short test summary info ============================
ERROR tests/test_dag_validation.py - TypeError: 'module' object is not callable
!!!!!!!!!!!!!!!!!!!! Interrupted: 1 error during collection !!!!!!!!!!!!!!!!!!!!
=============================== 1 error in 0.33s ===============================