fix unballenced parenthesis in docs
fix unballenced parenthesis in docs

jcmgray/xarray,shoyer/xarray,cpaulik/xray,pydata/xarray,markelg/xray,jhamman/xarray,jhamman/xray,markelg/xray,chunweiyuan/xarray,rabernat/xray,markelg/xray,NicWayand/xray,xray/xray,pydata/xarray,shoyer/xarray,pydata/xarray,drewokane/xray,rabernat/xray,petercable/xray,jhamman/xarray,jhamman/xarray,shoyer/xray,cpaulik/xray