docs: change argument name of output path

Author: uwzm

README.md

@@ -138,11 +138,11 @@ Since version 2.0.0 this client supports general OData models hosted by FROST se
 
 For this purpose the client provides a command line interface for generating a service module containing the URL of the FROST server in use as well as source code for the Python classes corresponding to the data model contained in the server. It is called like this:
 ```bash
-frost-codegen --url http://localhost:8080/FROST-Server/ODATA_4.01/ --out my_service_module
+frost-codegen --url http://localhost:8080/FROST-Server/ODATA_4.01/ --output-dir my_service_module
 ```
 or
 ```bash
-frost-codegen --url http://localhost:8080/FROST-Server/ODATA_4.0/ --out my_service_module
+frost-codegen --url http://localhost:8080/FROST-Server/ODATA_4.0/ --output-dir my_service_module
 ```
 making use of the OData 4.01 or OData 4.0 endpoint of the FROST server, respectively.