update check_journallog

docs/20_Checks/check_journallog.md

@@ -8,6 +8,11 @@ This check requires access to journalctl.
 ## Requirements
 
 * `journalctl` binary
+* sudo permissions to `journalctl`
+
+```txt
+icingaclient ALL=(ALL) NOPASSWD: /bin/journalctl
+```
 
 ## Syntax