DesktopmodeWindowDecorViewModel: Use Display Context.

Instead of using the default Context supplied, use the displayContext
from DisplayController associated with the TaskInfo's displayId.

Bug: 382023296
Test: Build
Flag: com.android.window.flags.enable_bug_fixes_for_secondary_display
Change-Id: I5493598ea4bce49c6b53a67526dd622abdc785d1