Add NavigationModeFeatureFlag am: 162ed05ac9

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Launcher3/+/13714559

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: Icab75bbd5a48df0348e2b8ec71e6ad37925d9b9b