Allow constructing a PIN LockscreenCredential with mInvalidChars am: 220d6a284e am: 9a3ec893bb

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

Change-Id: I3d95820ae19f277f990b021812167f164dfdaf19
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>