Renderer=AAT specifies non-existent shaper

[zauguin]

Description

This came up in https://github.com/latex3/luaotfload/issues/155#issuecomment-639029576: fontspec species the shaper coretext_aat if Renderer=AAT is given on LuaTeX. This shaper has been removed from HarfBuzz some time ago. AAT fonts should still be handled by the regular ot shaper or, on MacOS CoreText shaping can be requested by the coretext shaper (If that is compiled into HarfBuzz).

Check/indicate

• [ ] Relevant for XeTeX
• [X] Relevant for LuaTeX
• [ ] Issue tracker has been searched for similar issues?
• [ ] Links to <tex.stackexchange.com> discussion if appropriate

Minimal example demonstrating the issue

n/a (I don't have a Mac system to experiment with this)

Further details