Update WiFiGeneric.cpp (#7044)

Changes WiFi Static TX Cache Buffer Number to 4 in order to avoid issues with sending more than 1 packet at the same time.

libraries/WiFi/src/WiFiGeneric.cpp

@@ -668,7 +668,7 @@ bool wifiLowLevelInit(bool persistent){
 	    cfg.static_tx_buf_num = 0;
             cfg.dynamic_tx_buf_num = 32;
 	    cfg.tx_buf_type = 1;
-            cfg.cache_tx_buf_num = 1;  // can't be zero!
+            cfg.cache_tx_buf_num = 4;  // can't be zero!
 	    cfg.static_rx_buf_num = 4;
             cfg.dynamic_rx_buf_num = 32;
         }