Fix CameraPivot rotation in Moving the player with code (#6654)

CameraPivot should be rotated -45 degrees instead of 45 degrees
in order to produce the results demonstrated in the screenshots.
Otherwise, the camera will be pointing upwards instead of downwards.

getting_started/first_3d_game/03.player_movement_code.rst

@@ -375,7 +375,7 @@ one).
 
 |image7|
 
-Here's where the magic happens. Select the *CameraPivot* and rotate it ``45``
+Here's where the magic happens. Select the *CameraPivot* and rotate it ``-45``
 degrees around the X axis (using the red circle). You'll see the camera move as
 if it was attached to a crane.