Resolved error in validation.

Author: ajcerezo

components/cache/adapters/couchbasebucket_adapter.rst

@@ -99,10 +99,10 @@ option names and their respective values::
 Available Options
 ~~~~~~~~~~~~~~~~~
 
-``username`` (type: ``string``, default: ````)
+``username`` (type: ``string``)
     Username for connection ``CoucbaseCluster``.
 
-``password`` (type: ``string``, default: ````)
+``password`` (type: ``string``)
     Password of connection ``CouchbaseCluster``.
 
 ``operationTimeout`` (type: ``int``, default: ``2500000``)