plugins: mnclength missed mcc 289 for Abkhazia

It's strange that [ITU document](http://www.itu.int/dms_pub/itu-t/opb/sp/T-SP-E.212A-2012-PDF-E.pdf) doesn't have it, but it does exist on other sites, e.g. [Wikipedia](http://en.wikipedia.org/wiki/Mobile_country_code#A) and [mcclist.com](http://mcclist.com/mobile-network-codes-country-codes.asp#A).