Gracefully close pip window after test

Try to mitigate pip-dismiss-overlay leak

Test: atest WMShellFlickerTests
Bug: 258120818
Change-Id: Ifa94292612677d9acdcc2d87cd6c06d793708d81

libs/WindowManager/Shell/tests/flicker/src/com/android/wm/shell/flicker/pip/EnterPipOnUserLeaveHintTest.kt

@@ -61,6 +61,8 @@ class EnterPipOnUserLeaveHintTest(flicker: FlickerTest) : EnterPipTest(flicker)
                 pipApp.enableEnterPipOnUserLeaveHint()
             }
             teardown {
+                // close gracefully so that onActivityUnpinned() can be called before force exit
+                pipApp.closePipWindow(wmHelper)
                 pipApp.exit(wmHelper)
             }
             transitions { tapl.goHome() }