Fix that icons overlapped in Preview at Display size and text screen under Vision Settings.

Change the app grid view from 4 columns to 3 columns, and app count from 8 to 6.

Fix: 222241141
Test: manual test
Change-Id: I66c131be77971c9ccc3ee796a6732ff65aac01a5

res/layout/accessibility_text_reading_preview_app_grid.xml

@@ -20,8 +20,8 @@
     xmlns:app="http://schemas.android.com/apk/res-auto"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
-    android:numColumns="4"
+    android:numColumns="3"
     android:gravity="center"
     android:nestedScrollingEnabled="true"
     android:importantForAccessibility="noHideDescendants"
-    app:appCount="8"/>
+    app:appCount="6"/>