At the moment, we don’t have an option to hide the Phone field in the Wholesale Registration page.
But you can simply use the CSS code below to hide it. Please put this on your theme’s style.css to apply the change.
#wwlc-registration-form .wwlc_phone {display:none;}
Remember to make sure that the phone field is set to be ‘not required’ in the WooCommerce > Settings > Wholesale Lead tab > Built-in Fields sub-menu.