Allow constructing a PIN LockscreenCredential with mInvalidChars am: 220d6a284e

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/2775379

Change-Id: I7f4282a06c77e2dfab0a4380a7da2a8451f9e8c4
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>