public: update SPI links to https

Sadly it seems the SPI does not redirect http to https or implement hsts
so it's better to hardcode the links to https.
Signed-off-by: Jelle van der Waa <jelle@archlinux.org>

templates/public/donate.html

@@ -26,10 +26,10 @@ <h3>Monetary donations</h3>
     <p>Financial contributions are accepted via <a href="https://co.clickandpledge.com/Default.aspx?WID=47294" title="Donate via Click&amp;Pledge to Arch Linux">Click&amp;Pledge</a>
     or via <a href="https://www.spi-inc.org/projects/archlinux/" title="Donate via SPI to Arch Linux">SPI</a> directly using PayPal or Credit Card payment.
     Arch Linux is a member project of the
-    <a href="http://www.spi-inc.org/">Software in the Public Interest, Inc.</a>
+    <a href="https://www.spi-inc.org/">Software in the Public Interest, Inc.</a>
     non-profit corporation. Funds are used for hosting costs, server hardware
     upgrades, and more. You are encouraged to learn more about the SPI, as well
-    as <a href="http://www.spi-inc.org/donations/">how donations work</a>.</p>
+    as <a href="https://www.spi-inc.org/donations/">how donations work</a>.</p>
 
     <a href="https://co.clickandpledge.com/Default.aspx?WID=47294">
         <img src="{% static "click_and_pledge.png" %}" alt="Donate via Click&amp;Pledge to Arch Linux" title="Donate via Click&amp;Pledge to Arch Linux"/>