Remove attach-failed-due-to-SIP checks which were not working

The SIP debugserver was calling in attach_failed_due_to_sip
haven't worked for a while; remove them.  To check this
properly we'd need debugsever to call out to codesign(1) to
inspect the entitlements, or the equivalant API,
and I'm not interested in adding that at this point.  SIP
is has been the default on macOS for a couple of releases
and it's expected behavior now.

<rdar://problem/59198052>