Revert "Always report mandatory insets for button nav"

This reverts commit 4304a14206805a99b63a0a0079c3907ad7f6893d.

Reason for revert: Likely culprit for b/343564388  - verifying through ABTD before revert submission. This is part of the standard investigation process, and does not mean your CL will be reverted.

Change-Id: Ibc6fae27f31bcb54406da013babc76b2d5fc7f10
diff --git a/quickstep/src/com/android/launcher3/taskbar/TaskbarInsetsController.kt b/quickstep/src/com/android/launcher3/taskbar/TaskbarInsetsController.kt
index 6869ecd..4f511c1 100644
--- a/quickstep/src/com/android/launcher3/taskbar/TaskbarInsetsController.kt
+++ b/quickstep/src/com/android/launcher3/taskbar/TaskbarInsetsController.kt
@@ -223,7 +223,7 @@
             provider.insetsSize = getInsetsForGravityWithCutout(contentHeight, gravity, endRotation)
         } else if (provider.type == mandatorySystemGestures()) {
             if (context.isThreeButtonNav) {
-                // Leave null to inset by the window frame
+                provider.insetsSize = Insets.of(0, 0, 0, 0)
             } else {
                 val gestureHeight =
                         ResourceUtils.getNavbarSize(