Fix up SearchBarScrollingViewBehaviorTest to not use ColorDrawable

In a recent Material update [1] which was rolled into platform, the
background of the app bar layout was changed to return a
MaterialShapeDrawable instead of a ColorDrawable. This caused the tests
to fail, change it to the new type to fix the test.

[1] https://github.com/material-components/material-components-android/commit/1adc50110ed6491661f89aa535355b1480fac73a

Fix: 426209738
Test: atest SearchBarScrollingViewBehaviorTest
Flag: EXEMPT bug / test fix

Change-Id: I17959daec0eb39ebb05e242fdefc0e55aeaa6f59