Fix backspace key in Rpi SSH keyboard

There was a typo in the generated keycode.

src/platforms/rcore_drm.c

@@ -1556,7 +1556,7 @@ static void ProcessKeyboard(void)
         {
             CORE.Input.Keyboard.currentKeyState[259] = 1;
 
-            CORE.Input.Keyboard.keyPressedQueue[CORE.Input.Keyboard.keyPressedQueueCount] = 257;     // Add keys pressed into queue
+            CORE.Input.Keyboard.keyPressedQueue[CORE.Input.Keyboard.keyPressedQueueCount] = 259;     // Add keys pressed into queue
             CORE.Input.Keyboard.keyPressedQueueCount++;
         }
         else