Make tracking_id const inside PalmFilterStroke am: 301ae9d2a6

Original change: https://googleplex-android-review.googlesource.com/c/platform/external/libpalmrejection/+/19349205

Change-Id: If61a9c32390464f9d879f6339ce1488f17ff64f9
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>