Delete App Icons from Test Data Assets

Previously, the test assets were being pulled into the release APK.
Unfortunately, it isn't possible to build the Release APK from within
SysUi Studio. Since the tests don't test the image loading, I am opting
to simply delete the large image strings, rather than try to figure out
why the release APK is including these test assets.

Bug: 301105199
Test: The tests still pass. That being said, it is difficult to test
this other than see if the APK size doesn't get flagged for growing too
large. It should be ok though, since the test assets are now WAY
smaller.

Change-Id: Ic52bede8296624740e4ca1573955494c3b94bf87