I don't know where you will find it if it still exists. Ask your company? It is NOT a 'taxy' limit' - it is a wind speed above which a 737 ANYWHERE in the open needs (?used to need?) an engineering check. You could be sitting on stand;a/c parked overnight on the apron;taxying; whatever. Obviously headwinds as in 'flying' do not count. I assume it is to do with rudder maybe? Anyway, it isn't very likely to bother you.