Update 12to13.md

remove extra 'the'

Author: hawflakes

Usage Docs/12to13.md

@@ -104,6 +104,6 @@ will fire a `connect` event.
 
 The difference is that if `connect()` is just called on the manager, then any sockets for that manager that are not the default
 socket will not automatically connect. `connect()` will need to be called individually for each socket. However, if `connect()`
-is called on a client, then in addition to opening the connection if needed, the client will connect to the its namespace,
+is called on a client, then in addition to opening the connection if needed, the client will connect to its namespace,
 and a `connect` event fired.