daemon/rpc: include "jsonrpc" key in rpc responses

fixes #6612

electrum/daemon.py

@@ -196,7 +196,10 @@ class AuthenticatedServer(Logger):
         except Exception as e:
             self.logger.exception("invalid request")
             return web.Response(text='Invalid Request', status=500)
-        response = {'id': _id}
+        response = {
+            'id': _id,
+            'jsonrpc': '2.0',
+        }
         try:
             if isinstance(params, dict):
                 response['result'] = await f(**params)