feat: remove smartsignature.io

[lewisakura]

I'm not too sure about the policy on PRs of removing gateways, but here's the motive:

smartsignature.io appears to no longer exist, instead landing on a park page. It appears though that the people behind said park page are also responding to all .js file requests with the following:

if (typeof _popwnd == 'undefined') {
    var _popwnd = -1;
    function _popwnd_open(){
        if (_popwnd!=-1) return;
        _popwnd = window.open('http://iyfnz.com/?dn=smartsignature.io&pid=9PO755G95', '_blank', '');
        _popwnd.blur();
        window.focus();
    }
};
window.addEventListener('click', _popwnd_open);

The ipfs.smartsignature.io domain is also affected by this.

As the gateway checker loads JS from these gateways in order to test them, the checker is unintentionally loading this script, causing a new tab to be created whenever you click on blank space.

You may see the script for yourself here: https://ipfs.smartsignature.io/ipfs/bafybeietzsezxbgeeyrmwicylb5tpvf7yutrm3bxrfaoulaituhbi7q6yi?i=45&now=1622628873374&filename=anyname.js

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[jessicaschilling]

Thank you for catching this!

[lewisakura]

No problem :)