Info.plist: fix spelling of CFBundleTypeIconFile

This patch, coupled with [lsregister -kill](http://www.tuaw.com/2009/06/11/terminal-tips-rebuild-your-launch-services-database-to-clean-up/) to re-read the old Info.plist, yields Gnucash icons on *.ofx files.

Thanks for all your hard work on the app bundle - it's working well for me so far.