reworded comment

controller/predicates/is_request_sources_only_whosonfirst.js

@@ -1,6 +1,6 @@
 const _ = require('lodash');
 
-// returns true IFF clean.sources only contains 'whosonfirst'
+// returns true IFF 'whosonfirst' is the only requested source
 module.exports = (req, res) => (
   _.isEqual(
     _.get(req, 'clean.sources', []),