Removed unusable key

Author: NadavShaar

src/components/HeaderCellContainer.jsx

@@ -1,8 +1,8 @@
 import React from 'react';
 import { SortableElement, SortableHandle } from 'react-sortable-hoc';
 
-const SortableItem = SortableElement(({children, index, columnId, className}) => (
-    <div className={className} data-column-id={columnId} key={index}>{children}</div>
+const SortableItem = SortableElement(({children, columnId, className}) => (
+    <div className={className} data-column-id={columnId}>{children}</div>
 ));
 
 const SortableDragHandle = SortableHandle(({children, index}) => (