cd /usr/share/javascript/proxmox-widget-toolkit/

cp proxmoxlib.js proxmoxlib.js.bak

vim proxmoxlib.js

on line 563 you find

 if (res === null || res === undefined || !res || res
    .data.status.toLowerCase() !== 'active') {
    Ext.Msg.show({

change this to 

 if (false ) {
    Ext.Msg.show({

systemctl restart pveproxy

close your browser,connect to the server and you should find the subscription no longer appears