Fix AnimatedSprite doesn't emit animation_finished when changing playback direction

(cherry picked from commit d5f5e96e118d6904aaa071fcb8e8f08fa2d4eae5)

scene/2d/animated_sprite.cpp

@@ -599,6 +599,7 @@ void AnimatedSprite::play(const StringName &p_animation, const bool p_backwards)
 		}
 	}
 
+	is_over = false;
 	set_playing(true);
 }