If you don't want to designate a gender on your transcript, it's not required. As with any field in the student info section, if you do not put an entry in a designated field, it will not print on the transcript. 
If you do not designate a gender when filling out the student information section, then it is omitted from the student information section and doesn't show up on the printed transcript.
If you want to omit gender on transcripts that you have already created, click on Edit Student Info, then go to Gender and click on the white space above the gender choices, then scroll down to the very bottom and click on Save Changes. Now when you look at the transcript the line for gender will no longer show.