VE-1145: Handle global/local favicon

https://wikia-inc.atlassian.net/browse/VE-1145 @inez 
It turns out that we don't need this any longer due to the way in which Favicon has been reworked. We're now getting a URL to the image (either on central or on local wiki) that already has a CB value. As this file is changed, the cb in the image URL is changed, so passing it through wfReplaceImageServer is unnecessary.