Set Autocomplete Off for Partner Code Field in Registration of Web Store

1. Navigate to Setup > Site Builder > Customize Text
2. Message tab
3. Try to find If you have a partner or affiliate code, enter it here
4. In the Customization field, add the javascript below:

<script>
var partnerField = document.getElementById('regPartner');
partnerField.setAttribute("autocomplete", "off");
</script>

5. Save