Merge "Document the allowed challenge size" into main am: 4f73689e26 am: bcd81f14b8

Original change: https://android-review.googlesource.com/c/platform/hardware/interfaces/+/2813217

Change-Id: I199f9edff816d9f52de5bf1cf628bf3595a4879b
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>