Add missing translation string in broadlink (#127829)

homeassistant/components/broadlink/strings.json

@@ -43,6 +43,7 @@
     },
     "error": {
       "cannot_connect": "[%key:common::config_flow::error::cannot_connect%]",
+      "invalid_auth": "[%key:common::config_flow::error::invalid_auth%]",
       "invalid_host": "[%key:common::config_flow::error::invalid_host%]",
       "unknown": "[%key:common::config_flow::error::unknown%]"
     }