As Janel stated, you can remove buttons via the system properties but if you only want to adjust for a specific field, you can adjust on the attributes of field. For example, here is the OOB setup for the editor on Knowledge (go to dictionary entry for the Article Body field on kb_knowledge):
| editor.height=300,editor.plugins=table colorpicker textcolor link image media codemirror lists advlist fullscreen charmap directionality emoticons hr insertdatetime nonbreaking pagebreak print searchreplace wordcount anchor toc codesample visualblocks visualchars compat3x autolink align_listitems,editor.toolbar=fontselect fontsizeselect italic bold underline strikethrough forecolor backcolor pastetext removeformat | formatselect searchreplace undo redo | bullist numlist outdent indent alignleft aligncenter alignright | toc table link unlink image media codesample | code fullscreen | bold,encode_utf8=false,serializer=com.glide.script.TranslatedTextXMLSerializer |
by removing the "code" attribute, the button will no longer display on the editor:
