Why is chevron showing on child Data? Tree grid lwc salesforce

JS file

import { LightningElement, wire , track} from "lwc";
import { NavigationMixin } from 'lightning/navigation';
import { refreshApex } from '@salesforce/apex';

// Import the schema
import Name from "@salesforce/schema/User.Name";

import getAllTopManagers from "@salesforce/apex/ManagersHierarchy.getAllTopManagers";
import getManagers from "@salesforce/apex/ManagersHierarchy.getManagers";

const actions = 
 [
  { label: 'Edit', name: 'edit_record'}
 ];

const COLS = 
[
{fieldName: "Name", label: "Name", editable: true, hideDefaultActions: true},
{fieldName:"Weight__c", label:"Weight", editable: true, hideDefaultActions: true},
{type: 'action', label: '', typeAttributes: { rowActions: actions, menuAlignment: 
'right' }}
];



export default class WeightedRR extends NavigationMixin(LightningElement)
 {
gridColumns = COLS;
isLoading = true;
gridData = [];


@wire(getAllTopManagers)
parentAccounts({ error, data }) {
    if (error) {
        console.error("error loading Users", error);
    } else if (data) {
        this.gridData = data.map((user) => ({
            _children: [],
            ...user
        }));
        this.isLoading = false;
        
    }
}

handleOnToggle(event) {

    const rowName = event.detail.name;

    if (!event.detail.hasChildrenContent && event.detail.isExpanded) {
        this.isLoading = true;
        getManagers({parentId: event.detail.name})
            .then((result) => {
            
                if (result && result.length > 0) {
                    const newChildren = result.map((child) => ({
                        _children: [],
                        ...child
                    }));
                    this.gridData = this.getNewDataWithChildren(event.detail.name, 
    this.gridData,newChildren);
                } 
            })

            .finally(() => {
                this.isLoading = false;
            });

    }
}

getNewDataWithChildren(rowName, data, children) {

    return data.map((row) => {
        let hasChildrenContent = false;
        if (
            Object.prototype.hasOwnProperty.call(row, "_children") &&
            Array.isArray(row._children) &&
            row._children.length > 0
        ) {
            hasChildrenContent = true;
        }

        if (row.Id === rowName) {
            row._children = children;
        } else if (hasChildrenContent) {
            this.getNewDataWithChildren(rowName, row._children, children);
        }
        return row;
    });
 }
}