Add note for FLAG_CANCEL_CURRENT when stopping scan

Added a note in the Android API documentation for stopScan to make sure
that the flag FLAG_CANCEL_CURRENT is not used when creating the
PendingIntent parameter.

Bug: 77658091
Test: Just compile since not logic is changed
Change-Id: I55f33ae68679310ba4899708a2072a40fea0b3b4