Log when entry is saved for removal after expand

Fixes: 360188098
Bug: 359628765
Test: adb shell cmd statusbar echo -b NotifHeadsUpLog:verbose
      adb reboot
      adb logcat | grep HeadsUpManager
Flag: com.android.systemui.notification_avalanche_throttle_hun
Change-Id: I69363cfebc881a8fd8634463b6cc99359d11d9a5