[CrOS Bluetooth] Remove device->IsPaired() DCHECK() from DeviceCache.

Remove DCHECK() for device->IsPaired() in
DeviceCacheImpl::DeviceConnectedStateChanged(). This is because devices
that are paired in OOBE HID detection still have
device->IsPaired() == false when their connection state updates,
causing a crash.

Bug: b/214453934
Change-Id: I35bb74f33a8da9e673104adee601a65a3eeb1e64
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3389695


Commit-Queue: Gordon Seto <gordonseto@google.com>
Commit-Queue: Kyle Horimoto <khorimoto@chromium.org>
Auto-Submit: Gordon Seto <gordonseto@google.com>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/main@{#959308}