Remove unnecessary effects of wallpaper_open_exit

The translate animation should move the content outside the screen,
so the alpha effect is not visible. And the scale is always 1.
This also aligns the duration with wallpaper_open_enter to 225ms.

Bug: 151709552
Test: Finish a task which will return to an activity with wallpaper.
Change-Id: If1854a77de1410e65da478f2b4c5a645357e6053