Removed unnecessary invocation of Ethernet.maintain()

Since this example utilizes a statically assigned IP address, it is not necessary to call Ethernet.maintain().

libraries/Ethernet/examples/WebServer/WebServer.ino

@@ -97,7 +97,6 @@ void loop() {
     // close the connection:
     client.stop();
     Serial.println("client disconnected");
-    Ethernet.maintain();
   }
 }