Increase the uninstall button touch target size

Increase the touch target size of uninstall button in the unused apps
page by adding a padding to the image view. The view now has a 48dp by
48dp size but the icon size remains the same.

Bug: 188826765
Test: Built and flashed to device. Verify through hsv the touch target
is 48dp x 48dp

Change-Id: I20195912bec5272d9141a49bd79689deb06fe398