element 树形控件，父节点不显示复选框，子节点显示复选框，需增加特定样式

 代码复用参考：

/deep/
  .stafftree
  .el-tree
  .el-tree-node
  .is-leaf
  + .el-checkbox
  .el-checkbox__inner {
  display: inline-block;
}
/deep/ .stafftree .el-tree .el-tree-node .el-checkbox .el-checkbox__inner {
  display: none;
}
::v-deep.el-tree-node.is-current > .el-tree-node__content {
  background-color: #041a21 !important;
}