Remove the Billing VAT field from the checkout form only for Wholesalers.

functions.php

/**
 * Remove the Billing VAT field from the checkout form only for Wholesalers.
 */
function custom_override_checkout_fields( $fields ) {

    if ( ! current_user_can( 'wholesalers' ) && isset( $fields['billing']['billing_vat'] ) ) {
        unset( $fields['billing']['billing_vat'] );
    }

     return $fields;
}
add_filter( 'woocommerce_checkout_fields' , 'custom_override_checkout_fields' );