The Desktop Experience is only available (and therefore the freeform on
secondary display disabled) if the device is eligible for Desktop Mode.
Correcting the test to make it correct.
Fix: 393547201
Test: atest DesktopModeSecondaryDisplayPreferenceControllerTest
Flag: EXEMPT (bug fix)
Change-Id: I36a031487d8a6f6d681a2cb46a1fa50e47d870cc