Correct Pico Display 2 baud

The Pico Display 2 example specifies a baud of 74 * 1000 * 1000.
However, the highest baud the Raspberry Pi Pico can achieve is
62,500,000.

I checked and even when the baud of 74 * 1000 * 1000 is specified,
it ends up using the max that the Raspberry Pi Pico can handle anyway.

This commit removes the incorrect baud parameter, using the default
parameter instead.

libraries/pico_display_2/pico_display_2.cpp

@@ -49,7 +49,7 @@ namespace pimoroni {
     gpio_set_function(Y, GPIO_FUNC_SIO); gpio_set_dir(Y, GPIO_IN); gpio_pull_up(Y);
 
     // initialise the screen
-    screen.init(true, false, 74 * 1000 * 1000);
+    screen.init(true, false);
   }
 
   void PicoDisplay2::update() {