fix typoe

Author: zookzook

lib/mongo/session.ex

@@ -5,7 +5,7 @@ defmodule Mongo.Session do
   In case of MongoDB 3.6 or greater the driver uses sessions for each operation. If no session is created the driver will create a so-called implicit session. A session is a UUID-Number which
   is added to some operations. The sessions are used to manage the transaction state as well. In most situation you need not to create a session instance, so the api of the driver is not changed.
 
-  In case of multiple insert statemantes you can use transaction (MongoDB 4.x) to be sure that all operations are grouped like a single operation. Prerequisites for transactions are:
+  In case of multiple insert statements you can use transaction (MongoDB 4.x) to be sure that all operations are grouped like a single operation. Prerequisites for transactions are:
   MongoDB 4.x must be used as replica set or cluster deployment. The collection used in the operations must already exist. Some operation are not allowed (For example: create index or call count).
 
   ## Example