readme.md: fix wrong bracket ] in command

Author: istrator2

README.md

@@ -147,7 +147,7 @@ import requests
 key_data = {"domain": "ffmuc_welt","public_key": "o52Ge+Rpj4CUSitVag9mS7pSXUesNM0ESnvj/wwehkg="}
 broker_url = "http://127.0.0.1:5000"
 push_key = requests.get(f'{broker_url}/api/v1/wg/key/exchange', json=key_data)
-print(f'Key push was: {push_key.json().get("Message")]}')
+print(f'Key push was: {push_key.json().get("Message")}')
 ```
 
 ### Worker