[Python][CI] Enable S3 tests on macOS builds

[pitrou]

Describe the enhancement requested

S3 is enabled when building PyArrow for macOS (both on PR builds and in Crossbow wheel builds), but minio isn't installed before testing, therefore S3 support in PyArrow is not tested at all.

Component(s)

Continuous Integration, Python

[pitrou]

@raulcd @jorisvandenbossche

[pitrou]

Issue resolved by pull request 44129
#44129