fix tabs

Author: lindseymoore

source/connection/connection-pools.txt

@@ -45,7 +45,7 @@ string or by passing a ``MongoClientSettings`` object to the
 The following code creates a client with a maximum connection pool size of ``50`` 
 by using either a connection string or ``MongoClientSettings`` object:
 
-. tabs::
+.. tabs::
 
    .. tab:: Connection String
       :tabid: uri