Revert "Fix firefox event issue related to Button tag (#544)"

This reverts commit 6c7a90d.

Author: Claudéric Demers

src/SortableContainer/index.js

@@ -153,11 +153,7 @@ export default function sortableContainer(
          * prevent subsequent 'mousemove' events from being fired
          * (see https://github.com/clauderic/react-sortable-hoc/issues/118)
          */
-        if (
-          !isTouchEvent(event) &&
-          (event.target.tagName === NodeType.Anchor ||
-            event.target.tagName === NodeType.Button)
-        ) {
+        if (!isTouchEvent(event) && event.target.tagName === NodeType.Anchor) {
           event.preventDefault();
         }