drop Google Checkout link from SFC donation page

Google is discontinuing Checkout later this month, and SFC
has asked all member projects to drop any links.

Formatting-wise, this means we can drop the side-by-side
table entirely, and "Paypal" becomes just another item in
the list of <h3> sections.
Merge pull request #319 from peff/drop-google-checkout

drop Google Checkout link from SFC donation page