Previous issue for Python 3.6: #28450

We dropped Python 3.6 support in pyarrow 7.0 (early 2022). If we follow the same pattern, we can drop 3.7 support for pyarrow 13 (so we can start doing it after the 12.0 release), since by the time of that release it should have reached end of life (https://endoflife.date/python)