UpdatersExample negative width error in example scenes

### Describe the error
In the UpdatersExample in the [example scenes](https://3b1b.github.io/manim/getting_started/example_scenes.html), the line:
`lambda m: m.set_width(w0 * math.cos(self.time - now))` results in an error. In order for this to match the animation in the video it should read:
`lambda m: m.set_width(w0 * (math.cos(self.time - now - PI/2)+1))`

### Code and Error
**Code**:
UpdatersExample

**Error**:
manim\manimlib\mobject\mobject.py:903: RuntimeWarning: overflow encountered in double_scalars
self.scale(length / old_length, **kwargs)

### Environment
**OS System**: Windows 10
**manim version**: master manimGL v1.6.1
**python version**: Python 3.9.6