Disable flaky ModelDownloader integration tests. am: 5247b140e9 am: 69131b353c am: 1fe38576c5

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

Change-Id: I3561b27f59aab6f7a817be8da13641ebfe00ce9b
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>