Rectangle stroke has gaps

### Describe the bug
Rectangle and its subclasses cannot display their stroke (i.e. their sides) consistently. As the rendered rectangle's sides have some gaps rather show a consistent line

### Version
- Platform: Mac
- Python version: Python 3.9.12
- OpenGL version: 3.1.6
- manim version: ManimGL v1.6.1

### Codes and rendered results
``` python
Square(
side_length=1.,
stroke_color = WHITE,
stroke_width = 2.0,
fill_color = BLUE,
fill_opacity = 1.0,
).round_corners(0.15)
```