remove hardcoded topic_row_size

I can't believe this is still here haha

src/categories.js

@@ -62,7 +62,6 @@ var async = require('async'),
 				category.nextStart = results.topics.nextStart;
 				category.pageCount = results.pageCount;
 				category.isIgnored = results.isIgnored[0];
-				category.topic_row_size = 'col-md-9';
 
 				plugins.fireHook('filter:category.get', {category: category, uid: data.uid}, function(err, data) {
 					callback(err, data ? data.category : null);