Temporarily ignore ScreenDecorWindowTests

We need to implement mapping between PRIVATE_FLAG_IS_SCREEN_DECOR
windows and inset providers before these tests can pass.
Temporarily ignore them so we can flip the flag.

Test: n/a
Bug: 145242835
Bug: 118118435
Change-Id: Ib0960938c01c8408d355ddb919b5db8d65095905