This can easily be achieved by a small alteration to the widget. In the widget MPK, open the file 'CKEditorForMendix' and add the part I highlighted below: 'title: false' after line 239. Of course, do no forget to add a comma at the end of line 239 as well.
For more details about the CK Editor, see:
Either change the widget yourself or create an issue on github for this.
For more information on widget development see https://docs.mendix.com/howto/custom-widget-development/
What about changing the css and use somewhere display: none; ?