clatd: remove spurious MTU_DELTA define am: e4aa7b0879

Original change: https://android-review.googlesource.com/c/platform/external/android-clat/+/2490815

Change-Id: Ibb3fff42aed4f05a72e0bfb2d4a6b654e94dfe90
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>