Remove the launch root switch logic

The launch root switching logic is handled from the wm shell now. We
can remove the similar logic from the wm core.

Bug: 282712995
Test: atest ActivityStarterTests
Change-Id: I2e48c705a4ef50276935d28d79649af80e29622a

services/core/java/com/android/server/wm/ActivityStarter.java

@@ -2925,15 +2925,6 @@ class ActivityStarter {
             }
         }
 
-        // If the matching task is already in the adjacent task of the launch target. Adjust to use
-        // the adjacent task as its launch target. So the existing task will be launched into the
-        // closer one and won't be reparent redundantly.
-        final Task adjacentTargetTask = mTargetRootTask.getAdjacentTask();
-        if (adjacentTargetTask != null && intentActivity.isDescendantOf(adjacentTargetTask)
-                && intentTask.isOnTop()) {
-            mTargetRootTask = adjacentTargetTask;
-        }
-
         // If the target task is not in the front, then we need to bring it to the front...
         // except...  well, with SINGLE_TASK_LAUNCH it's not entirely clear. We'd like to have
         // the same behavior as if a new instance was being started, which means not bringing it