Should we deprecate get_sun

### What is the problem this feature will solve?

In #14354 we removed `get_moon` since it was nothing but a wrapper around `get_body`.

The case of `get_sun` is more complex; it provides an alternative method to `get_body(‘sun’)`. Both (by default) use `erfa.epv00` to find the relative position of Sun and Earth, but they differ in their handling of light travel time and aberration.

Arguably one is more correct than the other, and we should only retain the correct implementation? However in https://github.com/astropy/astropy/pull/14354#issuecomment-1419656506, @eerovaher pointed out that @eteq was strongly in favour of retaining `get_sun` in the past, so perhaps this needs more careful discussion?

### Describe the desired outcome

Only one way is provided of getting the Sun’s position

### Additional context

_No response_