panel: add margin above buttons

Author: v4hn

visualization/motion_planning_tasks/src/task_panel.ui

@@ -28,6 +28,9 @@
    </property>
    <item>
     <layout class="QHBoxLayout" name="tool_buttons_layout">
+     <property name="topMargin">
+      <number>2</number>
+     </property>
      <item>
       <spacer name="spacer">
        <property name="orientation">