Added comment to MongoClientOptions.Builder.codecRegistry to note that DB/DBCollection do not use the registry.
Added comment to MongoClientOptions.Builder.codecRegistry to note that DB/DBCollection do not use the registry.

 JAVA-1675

rozza/mongo-java-driver,jsonking/mongo-java-driver,kay-kim/mongo-java-driver,gianpaj/mongo-java-driver,jyemin/mongo-java-driver,rozza/mongo-java-driver,jsonking/mongo-java-driver,PSCGroup/mongo-java-driver,jyemin/mongo-java-driver