[E2E test] Ensure that opening a trampoline task in DW only triggers the task limit once

Bug: 410480799
Flag: EXEMPT no flag is needed for instrumented test
Test: atest PlatformScenarioTests:com.android.wm.shell.functional.OpenTrampolineAppInDesktopModeTest

Change-Id: I430fa231c7dc0b63e5fddac97ffd19012dd334a6