Disable flaky ModelDownloader integration tests. am: 5247b140e9 am: 30c4f79145

Original change: https://googleplex-android-review.googlesource.com/c/platform/external/libtextclassifier/+/23472318

Change-Id: I3dae81dd48965833b15da5406a236984d5474bf5
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>