Replace references in august strings.json (#40993)

homeassistant/components/august/strings.json

 {
   "config": {
     "error": {
-      "unknown": "Unexpected error",
-      "cannot_connect": "Failed to connect, please try again",
-      "invalid_auth": "Invalid authentication"
+      "unknown": "[%key:common::config_flow::error::unknown%]",
+      "cannot_connect": "[%key:common::config_flow::error::cannot_connect%]",
+      "invalid_auth": "[%key:common::config_flow::error::invalid_auth%]"
     },
     "abort": {
-      "already_configured": "Account is already configured",
+      "already_configured": "[%key:common::config_flow::abort::already_configured_account%]",
       "reauth_successful": "Re-authentication was successful"
     },
     "step": {