Cleanup exclude_task_from_recents flag.

The flag exclude_task_from_recents (com.android.window.flags) is
eligible for cleanup. Remove the flag and its references from the
codebase.

Bug: 388630258
Bug: 404726350
Bug: 428613086
Flag: EXEMPT cleanup
Test: atest WMShellMultivalentTestsOnDevice:BubbleControllerTest
Test: atest WMShellMultivalentTestsOnDevice:BubbleExpandedViewTest
Test: atest WMShellMultivalentTestsOnDevice:BubbleTaskStackListenerTest
Test: atest WMShellMultivalentTestsOnDevice:BubbleTaskViewListenerTest
Test: atest WMShellRobolectricTests:BubbleControllerTest
Test: atest WMShellRobolectricTests:BubbleExpandedViewTest
Test: atest WMShellRobolectricTests:BubbleTaskStackListenerTest
Test: atest WMShellRobolectricTests:BubbleTaskViewListenerTest
Test: atest WMShellUnitTests:BubbleTransitionsTest
Test: atest WMShellUnitTests:BubbleUtilsTest
Test: atest WMShellUnitTests:DesktopModeWindowDecorViewModelTests
Test: atest WMShellUnitTests:TaskViewTransitionsTest
Test: atest WmTests:RecentTasksTest
Test: atest WmTests:WindowContainerTransactionTests
Test: atest WmTests:WindowOrganizerTests
Change-Id: Ib03466b90b33fb9a1c928a01214e7a1bfc186517