Fix vector value in bullet example in Instancing with signals (#8203)

tutorials/scripting/instancing_with_signals.rst

@@ -30,7 +30,7 @@ given velocity:
 
     extends Area2D
 
-    var velocity = Vector2.ZERO
+    var velocity = Vector2.RIGHT
 
     func _physics_process(delta):
         position += velocity * delta
@@ -41,7 +41,7 @@ given velocity:
 
     public partial class Bullet : Area2D
     {
-        public Vector2 Velocity { get; set; } = Vector2.Zero;
+        public Vector2 Velocity { get; set; } = Vector2.Right;
 
         public override void _PhysicsProcess(double delta)
         {