hh: Don't send SET IDLE

SET IDLE command is deprecated in HID spec v1.1.1 (adopted in 2015).
Furthermore, this might race with the reply of GET REPORT or other
commands from UHID.

Therefore, let's not send this command.

Bug: 307923455
Bug: 369310847
Test: m -j
Test: Pair with a Keychron KB and plug in a security key.
      Verify the security key is usable.
Flag: com.android.bluetooth.flags.dont_send_hid_set_idle
Change-Id: I984a67a4203edb4564b48da3c74343bc86e65ebc