Temporarily disable failing IconTest.testParcel on Ravenwood

New code in Icon.java now relies on DesktopExperienceFlags, which
doesn't work on Ravenwood yet.

Disabling the test on Ravenwood, while a fix forward is investigated.

Fixes: 432119346
Test: atest FrameworksCoreTestsRavenwood android.graphics.drawable.IconTest#testParcel
Flag: EXEMPT test only change
Change-Id: I3dd646b1c3b36aabb7f139cbbb90f5755b8033cd