Undeprecate storage directory APIs

Android 10 did not support file path operations for apps in
scoped storage. But Android 11 and above do support file path
operations for such apps.

Undeprecate getExternalStorageDirectory() and
getExternalStoragePublicDirectory() to reflect the current level of
support.

BUG: 153562415
Test: m
Change-Id: Ibd93ca07a0c08b11a82b70dca8c2cd7d49600354
(cherry picked from commit 74bf4e68)