Update in_a_nutshell.rst

doc/in_a_nutshell.rst

@@ -4,7 +4,7 @@ OPC UA in a nutshell
 OPC UA, a collection of services
 --------------------------------
 
-In OPC-UA, all communication is based on service calls, each consisting of a request and a response
+In OPC UA, all communication is based on service calls, each consisting of a request and a response
 message. Be careful to note the difference between services and methods. Services are pre-defined in
 the standard and cannot be changed. But you can use the *Call* service to invoke user-defined
 methods on the server.