update doc

apps/schematic/api/README.md

@@ -43,4 +43,4 @@ You could open your browser here:
 ```
 https://localhost:7443/api/v1/ui/
 ```
-Note: When the OpenAPI description has changed, regenerate the REST API with nx run schematic-api:generate
+Note: When the OpenAPI description has changed, regenerate the REST API with nx run schematic-api:generate. Also, `dhparam.pem` was generated by using command: `RUN openssl dhparam -out dhparam.pem 4096`. If there's an issue with the `dhparam.pem` in the future, please re run the command.