[lldb] Tighten ABI assert in `StopInfoMachException::DeterminePtrauthFailure` (NFC) (#95015)

This patch tightens the assert check for the ABISP object in
`StopInfoMachException::DeterminePtrauthFailure`.

This causes some failure when debugging on a system that doesn't have
pointer authentification support, like on Intel for instance.

rdar://129401926



Signed-off-by: Med Ismail Bennani <ismail@bennani.ma>