Remove flaky read_fileNotFoundException test

Test: https://android-build.corp.google.com/abtd/run/L38500030003716467/
      (reproduce flake count was 20, and 
      com.android.systemui.communal.data.backup all passed)
Bug: 336561027
Fix: 336561027
Flag: n/a
Change-Id: I34abe501d6a79cc7daf7763353ffd0e1ae1fdece