[1] replaced the "Add Folder" a11y label by a tooltip.
However, this doesn't work and Orca doesn't read the row
properly; it simply says "not selected". The a11y label
already didn't work prior to [1].
To fix this, transform the tooltip into a GtkLabel. Also,
make the row to have the same padding so it's consistent
with the "Add Input Source..." row from Keyboard > Input
Methods.
[1] 00d9cd012f
7a210d3054