espnow: fix the bug for calling esp_wifi_set_channel(), this function only can be called after Wi-Fi started and sniffer enabled.

examples/wifi/espnow/main/espnow_example_main.c

@@ -62,12 +62,6 @@ static void example_wifi_init(void)
     ESP_ERROR_CHECK( esp_wifi_set_mode(ESPNOW_WIFI_MODE) );
     ESP_ERROR_CHECK( esp_wifi_start());
 
-    /* In order to simplify example, channel is set after WiFi started.
-     * This is not necessary in real application if the two devices have
-     * been already on the same channel.
-     */
-    ESP_ERROR_CHECK( esp_wifi_set_channel(CONFIG_ESPNOW_CHANNEL, 0) );
-
 #if CONFIG_ENABLE_LONG_RANGE
     ESP_ERROR_CHECK( esp_wifi_set_protocol(ESPNOW_WIFI_IF, WIFI_PROTOCOL_11B|WIFI_PROTOCOL_11G|WIFI_PROTOCOL_11N|WIFI_PROTOCOL_LR) );
 #endif