Update introduction.txt

Some minor copy edits for a bulleted list

Author: James Hansen

source/introduction.txt

@@ -90,9 +90,9 @@ High Availability
 MongoDB's replication facility, called :doc:`replica set
 </replication>`, provides:
 
-- *automatic* failover and
+- *automatic* failover
 
-- data redundancy.
+- data redundancy
 
 A :doc:`replica set </replication>` is a group of
 MongoDB servers that maintain the same data set, providing redundancy