esp_wifi: update esp_wifi_internal_set_fix_rate usage

components/esp_wifi/include/esp_private/wifi.h

@@ -251,6 +251,7 @@ esp_err_t esp_wifi_internal_set_sta_ip(void);
   *
   * @attention 1. If fixed rate is enabled, both management and data frame are transmitted with fixed rate
   * @attention 2. Make sure that the receiver is able to receive the frame with the fixed rate if you want the frame to be received
+  * @attention 3. Not support to set fix rate for espnow and 80211_tx
   *
   * @param  ifx : wifi interface
   * @param  en : false - disable, true - enable