Disable broken test on Fuchsia
Disable broken test on Fuchsia

This disables the ImageTest.SourceCubeTargetRenderbuffer test
that does not work on Fuchsia.

BUG=angleproject:2475, angleproject:3145
TEST=angle_end2end_tests on Fuchsia

Change-Id: I8e681926ee322642b39c32b3bc0cd266ffa1d11f
Reviewed-on: https://chromium-review.googlesource.com/c/1479283
Reviewed-by: Jamie Madill <7e492b4f1c8458024932de3ba475cbf015424c30@google.com>
Commit-Queue: Jamie Madill <7e492b4f1c8458024932de3ba475cbf015424c30@google.com>

ppy/angle,ppy/angle,ppy/angle,ppy/angle