TST: Use test_all again in devdeps #15242

I changed it to this in #15235 because not all packages catches up to numpy 2.0.dev breaking changes fast enough (e.g., skyfielders/python-skyfield#896) and also Python 3.12.

When numpy 2.0 and Python 3.12 both become stable and widely supported, maybe we can change it back to "test_all" for the devdeps job.

Blocked by:

• Compatibility with Numpy 2.0 and Python 3.12 skyfielders/python-skyfield#898