Centeralize items in a row in share sheet

The weight sum is wrong, it should be 3 as we have 3 "SpaceLayout"
in between 4 items. Indeed, we do not need to specify weightSum
explicitly, the UI framework will do it for us.

Fix: 68978578

Test: Build and observe the padding

Change-Id: I39fc73a0cfb1b557021a9393ff92dd76340b5f22