Rendering artifacts when rendering `ImplicitFunction` with OpenGL

Nobody has claimed this yet.

## Description of bug / unexpected behavior
With the following code:

```py
class ImplicitFunctionDemo(Scene):
def construct(self):
plane = NumberPlane()
curve = ImplicitFunction(
lambda x, y: (x**2 + y**2)**2 - 42*(x**2 - y**2),
color=YELLOW,
max_quads=5000,
)
self.add(plane)
self.add(curve)
```

The following is rendered on my PC:


As you can see there are many artifacts around the plotted curve.
## Expected behavior

## How to reproduce the issue

Code for reproducing the problem

```py
Paste your code here.
```

## Additional media files

Images/GIFs

## Logs
Terminal output

```
PASTE HERE OR PROVIDE LINK TO https://pastebin.com/ OR SIMILAR
```

## System specifications

System Details

- OS (with version, e.g Windows 10 v2004 or macOS 10.15 (Catalina)):
- RAM:
- Python version (`python/py/python3 --version`):
- Installed modules (provide output from `pip list`):
```
PASTE HERE
```

LaTeX details

+ LaTeX distribution (e.g. TeX Live 2020):
+ Installed LaTeX packages:

FFMPEG

Output of `ffmpeg -version`:

```
PASTE HERE
```

## Additional comments

Reproduce the provided ImplicitFunction scene with the OpenGL renderer and start by tracing the ImplicitFunction rendering path. Compare the rendered curve with the expected plot and identify the rendering behavior that produces the artifacts; done means the supplied example renders without the visible artifacts.

Written by the indexing model from the issue text.