Remove dropshadow from flip-view-buttons

Author: petetnt

src/styles/brackets.less

@@ -513,8 +513,6 @@ a, img {
             background-origin: content-box;
             -webkit-transform: translateZ(0); // forces GPU mode for better filter rendering on retina
             transform: translateZ(0); // future proofing
-            -webkit-filter: drop-shadow(0 1px 0 rgba(0,0,0,0.36));
-            filter: drop-shadow(0 1px 0 rgba(0,0,0,0.36));
             z-index: 1;
             vertical-align: middle;