Astropy 6.0.0 and moved astropy.coordinates.angle_utilities

[RuneDominik]

With the astropy 6.0.0 release the astropy.coordinates module was consolidated in #15220 and thus astropy.coordinates.angle_utilities no longer exists, resulting in failing CI jobs (e.g #253). According to astropy's PR this should be an easy fix by simply importing from astropy.coordinates which should even be backwards compatible at least to astropy v5.

As we currently require astropy>=4.0.2 we could however think of either fixing and/or updating the version to maintain comparability with other cta-observatory packages.

[maxnoe]

Same change done in ctapipe: cta-observatory/ctapipe#2475