[Companion] Don't promise call back on javadoc

We only stop scanning on timeout but don't limit the time the
user has to select a device.
So timeout != failure. Cleaning that up from javadoc to avoid confusion

Fixes: 74080737
Test: proofread
Change-Id: I36b2d96f85c3c15c20742b954a0b34956f23d6f8