Use default language levels, or use a number tip (#6037)

src/Commands/core/WatchdogCommands.php

@@ -325,7 +325,7 @@ protected function where(?string $type = null, $severity = null, ?string $filter
                 foreach ($severities as $key => $value) {
                     $levels[] = "$value($key)";
                 }
-                $msg = "Unknown severity level: !severity\nValid severity levels are: !levels.";
+                $msg = "Unknown severity level: !severity\nValid severity levels are: !levels.\nEither use the default language levels, or use a number.";
                 throw new \Exception(dt($msg, ['!severity' => $severity, '!levels' => implode(', ', $levels)]));
             }
             $conditions[] = "severity $operator :severity";