Fixed pause screen defaulting to be up on game launch

scenes/game_manager.tscn

@@ -19,6 +19,7 @@ size_flags_vertical = 3
 [node name="pause_menu" type="Panel" parent="UI"]
 pause_mode = 2
 unique_name_in_owner = true
+visible = false
 anchor_right = 1.0
 anchor_bottom = 1.0
 rect_pivot_offset = Vector2( 989, 509 )