Remove sysprop/pan.sysprop

The sysprop "bluetooth.pan.nap.enabled" was made when
"bluetooth.profile.pan.nap.enabled" has long since existed.

This CL removes the newly created one, including the file
where it is defined.

Bug: 305785609
Test: m -j;
Flag: EXEMPT, duplicate sysprop removal - it should be no-op ideally
Change-Id: I33fec7ff1c2a5fd115a0a20452c9bb33f3dd5d95