wp-content/plugins/woocommerce/includes/gateways/paypal/class-wc-gateway-paypal.php

$icon = ‘https://www.paypalobjects.com/webstatic/mktg/logo/AM_mc_vs_dc_ae.jpg’;

Addjust size in the theme CSS:
li.payment_method_paypal img {
height: 55px;
}

or remove image:

li.payment_method_paypal img {
display: none;
}