Remove ugly background images of buttons when changing search result columns.
Can be seen on https://bugzilla.wikimedia.org/colchange.cgi

Bug: 54823
Change-Id: I74672a04549e603d0f0a029c7795dc42f76a1e63
Merge "Remove ugly background images of buttons when changing search result columns. Can be seen on https://bugzilla.wikimedia.org/colchange.cgi"