Update "No items" message position to fix invisible bug

Because recent root have many header rows include chip and
apps row, it will cause inflated message text is not visible on
top.
Fix it by set inflated message align top instead center.

Fix: 124066041
Test: visual
Test: atest DocumentsUITests
Change-Id: I7cdcfd6f09471894ee786a024b47f0b3de9aaf91