How to disable visual button on admin site text area

[taihushui]

Hi, my version of abantecart is 1.2.12. The visual button mess up and auto remove my css style code on HTML code, how to disable or remove the visual button on text area?
I modified the code of admin/view/default/template/form/text_editor.tpl, remove the visual code, but nothing changed at all? Where should I change the code? Please help. Thank you.