#3661 unmount arrows when dropdown closes and got rid of duplicate element id

Author: chpy04

src/frontend/src/pages/GanttPage/GanttChart/GanttChartComponents/GanttTaskBar/GanttTaskBarDisplay.tsx

@@ -148,7 +148,7 @@ const GanttTaskBarDisplay = <T,>({
   };
 
   return (
-    <div id={task.id} style={ganttTaskBarContainerStyles()}>
+    <div style={ganttTaskBarContainerStyles()}>
       <Box sx={ganttTaskBarBackgroundStyles(days.length)}>
         <ArcherElement
           id={task.id}

src/frontend/src/pages/GanttPage/GanttChart/GanttChartComponents/GanttTaskBar/GanttTaskBarView.tsx

@@ -53,7 +53,7 @@ const GanttTaskBarView = <T,>({
         highlightTaskComparator={highlightTaskComparator}
       />
 
-      <Collapse in={showChildren}>
+      <Collapse in={showChildren} unmountOnExit>
         {task.children.map((child) => {
           return (
             <GanttTaskBar