As I said above you can remove progress property from the objects in the data array (and the progress will not be shown):
 
const tasks = [
  {
    id: 1,
    start: new Date(2024, 3, 2),
    end: new Date(2024, 3, 17),
    text: 'Project planning',
    // progress: 30,
    parent: 0,
    type: 'summary',
    open: true,
    details: "Outline the project's scope and resources.",
  },
  {
    id: 10,
    start: new Date(2024, 3, 2),
    end: new Date(2024, 3, 5),
    text: 'Marketing analysis',
    // progress: 100,
    parent: 1,
    type: 'task',
    details: 'Analyze market trends and competitors.',
  }
]
Please follow the example: https://stackblitz.com/edit/vitejs-vite-nkmprj5z?file=src%2Fdata.js,src%2FGanttComponent.jsx