Disable flaky ModelDownloader integration tests. am: 5247b140e9

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

Change-Id: Id66dc5b07792ad3c94473734760f952ad81e8e5b
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>