Update bt_app_av.c

[Tonymac32]

The demo increases the volume every so many seconds, remove that "feature"

[MARKANDEY-MAITHANI]

tatic void volume_change_simulation(void *arg)
{
ESP_LOGI(BT_RC_TG_TAG, "start volume change simulation");

for (;;) {
    /* volume up locally every 10 seconds */
    vTaskDelay(10000 / portTICK_RATE_MS);
     uint8_t volume = (s_volume + 5) & 0x7f;    /// 
    volume_set_by_local_host(volume);
}

}
In this line do not add anything with s_volume
like uint8_t volume = s_volume & 0x7f;