Remove warning about cases where root is null

We didn't see any issues for that since the introduction of this class
so we can just remove the warning.

Bug: 175627594
Test: N/A
Change-Id: Ibe2a0e57b859d67793f2206f556cf4005dd06f42

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

@@ -126,10 +126,6 @@ class TaskLaunchParamsModifier implements LaunchParamsModifier {
             root = activity;
         }
 
-        // TODO: Investigate whether we can safely ignore all cases where we don't have root
-        // activity available. Note we can't know if the bounds are valid if we're not sure of the
-        // requested orientation of the root activity. Therefore if we found such a case we may need
-        // to pass the activity into this modifier in that case.
         if (root == null) {
             // There is a case that can lead us here. The caller is moving the top activity that is
             // in a task that has multiple activities to PIP mode. For that the caller is creating a