The folder is locked, possibly by a file explorer you might have open that’s looking at the contents inside the webcache folder? Or the EpicLauncher is still running and locking it?
Try closing all windows except the file explorer you have webcache selected in to delete it and try again, make sure the epic launcher is closed again and try delete it again … and lastly, see if EpicLauncher is running by looking at the task manager and end process (then try delete the folder again)
Launch the task manager by rightclicking on your clock and picking ‘task manager’ … or by pressing CTRL+SHIFT+ESC or by pressing ALT+CTRL+DEL and picking ‘Task Manager’ there … then go to the details, find EpicGamesLauncher, select it an
d click ‘End Task’