[WindowDecor] Fix incorrect WindowDecorContext in MaximizeMenu UI

so that when the system language is changed, the context will have the
right locale so that the menu buttons' language is correctly set, even
when the task window is open.

Recall: http://recall/clips/447844af-c2b5-4557-85d1-6e95c24902ae

Bug: 414808810
Test: atest DesktopModeWindowDecorationTests
Flag: EXEMPT bugfix
Change-Id: I836f0785214579ef572e87416577051ea5326912