Remove mention of Generator in CachingIterator comments
Remove mention of Generator in CachingIterator comments

This was overlooked from 52df7a112e760b595a3485f50c23adf0591b95e8

jmikola/mongo-php-library-prototype,jmikola/mongo-php-library,jmikola/mongo-php-library,mongodb/mongo-php-library,mongodb/mongo-php-library,jmikola/mongo-php-library,jmikola/mongo-php-library,mongodb/mongo-php-library,mongodb/mongo-php-library,10gen-labs/mongo-php-library-prototype