VE-1146: Removing anything releated to Favicon in CreateWiki

https://wikia-inc.atlassian.net/browse/VE-1146 @inez 

This script doesn't appear to actually create a Favicon - that work has traditionally been happening with the importStarter() method which imports the starter database and all of its files. starter.wikia.com does not have its own Favicon.ico file, so Favicon.ico files are not created on new wikis. The starter on devboxes does have a Favicon.ico (which threw me off for a while), and Favicons are being created on devboxes. There is no need to set $wgFavicon on new wikis (we have retired that functionality with VE-1145) and no need to try creating a Favicon.