remove dead Gittip widget

Context: liberapay/liberapay.org#62

filippo.fly.dev/filippo.io/Heartbleed/faq.html

@@ -199,7 +199,7 @@ <h3><a name="donate" href="#donate">Can I send something your way?</a></h3>
                 <img alt="" border="0" src="https://www.paypalobjects.com/it_IT/i/scr/pixel.gif" width="1" height="1">
                 </form>
                 <br>
-                <script data-gittip-username="FiloSottile" data-gittip-widget="button" src="//gttp.co/v1.js"></script><br>
+
                 <a class="coinbase-button" data-code="b0b690c431f738f85fbbef8f860bd9e7" data-button-style="custom_small" href="https://coinbase.com/checkouts/b0b690c431f738f85fbbef8f860bd9e7">Donate Bitcoins</a><script src="https://coinbase.com/assets/button.js" type="text/javascript"></script><br>
                 <script id='fb1wlqo'>(function(i){var f,s=document.getElementById(i);f=document.createElement('iframe');f.src='//api.flattr.com/button/view/?uid=FiloSottile&button=compact&url=http%3A%2F%2Ffilippo.io%2FHeartbleed';f.title='Flattr';f.height=20;f.width=110;f.style.borderWidth=0;s.parentNode.insertBefore(f,s);})('fb1wlqo');</script><br>
                 Bitcoin address: 1A8gzd6HebEbNFkKpTJpLqbk98SHTjzJTJ (<a href="https://chart.googleapis.com/chart?cht=qr&chl=bitcoin%3A1A8gzd6HebEbNFkKpTJpLqbk98SHTjzJTJ&choe=UTF-8&chs=300x300">QR</a>)