Clean up transparent activity test in SizeCompatTests

We should be returning false for fillsParent() on the transparent activity.

Fix: 274749083
Test: atest WmTests:SizeCompatTests#testTranslucentActivitiesDontGoInSizeCompatMode
Change-Id: I6fb48f1d2768a86972eb22483077974c175c15b5

services/tests/wmtests/src/com/android/server/wm/SizeCompatTests.java

@@ -398,7 +398,7 @@ public class SizeCompatTests extends WindowTestsBase {
                 .setLaunchedFromUid(mActivity.getUid())
                 .setScreenOrientation(SCREEN_ORIENTATION_PORTRAIT)
                 .build();
-        doReturn(true).when(translucentActivity).fillsParent();
+        doReturn(false).when(translucentActivity).fillsParent();
         mTask.addChild(translucentActivity);
         // It should not be in SCM
         assertFalse(translucentActivity.inSizeCompatMode());