BlockingAdapter: remove STATE_UNKNOWN

STATE_UNKNOWN was an attempt to enforce we are not in a transitionary
state, but "isLeEnabled" already does that.
This state is currently miss-behaving if the test start while bluetooth
is already off.

Bug: 404722316
Fix: 404722316
Test: atest CtsRangingTestCases
Flag: TEST_ONLY
Change-Id: I3546a3f8628d6c87fa26a28e6a9fbf8604734a1e