Skip finishing menu activity when dismissing PiP

- The finishing activity triggers a race in which the next layout may
  relayout the PiP window in fullscreen. As a workaround, this just
  skips finishing the menu activity, which also reverts to the O dismiss
  animation (as in there is none).

Bug: 77730018
Test: Open PiP, dismiss it
Change-Id: I9c9ccf69e50fac516339bf497cfed4bf6dc26467