Calculate task height directly off portrait height

Change task height calculation implementation to be directly based off
device height in portrait mode. This allows the recycler view
layout manager's job to be simpler while still ensuring that task height
changes dynamically based off device configuration changes.

Bug: 114136250
Test: Go to recents Go, task height is based off portrait mode height
Change-Id: I9c7cada3b89d2b2cea5ece8c357a40ce5974a2e6
(cherry picked from commit 3172c681)