[RESTRICT AUTOMERGE] Add import of MAX_APP_TRANSITION_DURATION

The commit at ag/10876662 did not contain a required import. This change
fixes the build.

Bug: 145728687
Test: `mma` in frameworks/base/services/core/java/com/android/server/wm/

Change-Id: Ic37e2dc8498b0f6f5308653f4f9935038a486001
(cherry picked from commit 4236b3e8)