Hello,
First of all, thank you for your purchase.
I was able to remove the link button if I added the following CSS to my test site:
#mceu_9
{display:none;}
Please check this tutorial on how to add CSS to your website: https://www.wpbeginner.com/plugins/how-to-easily-add-custom-css-to-your-wordpress-site/
If this is not working for you, please send me the URL of the form where I can see it on your website and I will check it and provide a customized solution for you. However, the above solution should also work.
Regards, Szabi – CodeRevolution.