fix multiselct overflow bug

sass/modules/_managelists.sass

@@ -492,7 +492,6 @@
   +pie-clearfix
   +box-sizing(border-box)
   +box-shadow(rgba($blue-dark,$xsmall) 0 0 $xsmallem inset)
-  position: relative
   border: 1px solid $blue
   height: rhythm(12)
   background: rgba($blue-dark,$xxxsmall)

static/css/screen.css

@@ -3894,7 +3894,6 @@ footer[role="contentinfo"] small {
   -webkit-box-shadow: rgba(75, 87, 101, 0.382) 0 0 0.382em inset;
   -o-box-shadow: rgba(75, 87, 101, 0.382) 0 0 0.382em inset;
   box-shadow: rgba(75, 87, 101, 0.382) 0 0 0.382em inset;
-  position: relative;
   border: 1px solid #516985;
   height: 19.416em;
   background: rgba(75, 87, 101, 0.146);